JP7650317B2 - Stormwater drainage devices and systems - Google Patents

Description

The present invention relates to a rainwater drainage device and a rainwater drainage system that collects and drains rainwater.

In recent years, as the frequency of heavy rainfall has increased, storm water pipes have become larger in size in order to efficiently drain rainwater from the roofs of buildings.

In response to this, a rainwater drainage method is being used that uses the siphon effect to enable the use of smaller diameter rainwater pipes and a reduction in the number of rainwater standpipes.

For example, Patent Document 1 discloses a siphon-type rainwater drainage device that can drain large amounts of rainwater extremely efficiently by using siphon action during heavy rain, without increasing costs or damaging the appearance of the house.

JP 2004-308399 A (Patent No. 4130616 A)

However, the above-mentioned conventional rainwater drainage system has the following problems.
That is, in the rainwater drainage device disclosed in the above publication, the upper end of a siphon pipe having an opening area of 3 to 13 cm2 and arranged vertically along the exterior wall material of the house is connected to the bottom of a water collection pipe attached to the eaves.

Although this configuration allows rainwater to be efficiently drained by the siphon action, depending on how the rainwater flows into the siphon pipe, it may not be possible to create a full flow state inside the pipe, or an air column may form in the center of the rainwater that flows into the pipe in a vortex shape, reducing the efficiency of drainage.

The objective of the present invention is to provide a rainwater drainage device that can effectively generate a siphon effect in a drainage pipe and eliminate factors that inhibit the generation of the siphon effect, thereby enabling rainwater to be efficiently drained.

The rainwater drainage device according to the first invention is a rainwater drainage device that collects rainwater and drains it from a drain pipe, and includes a base and a lid. The base has a bottom surface and a drop outlet connected to the drain pipe. The lid faces the drop outlet and is disposed with a predetermined gap from the bottom surface. If the size of the gap is h and the inner diameter of the drop outlet is a, the following relational expression (1) is satisfied, and the size of the gap h is 20 mm or more.
0.22≦h/a≦0.37 (1)

The rainwater drainage device of the second invention is the rainwater drainage device of the first invention, and has a plurality of fins that are arranged on the outer periphery of the bottom surface of the base and are arranged at equal angular intervals around the drop outlet .

The rainwater drainage device of the third invention is the rainwater drainage device of the first or second invention, wherein fins are arranged radially along an imaginary circle inscribed in the surface of the lid portion, and the outer peripheral ends of the fins protrude from the outer edge of the lid portion .

The rainwater drainage device according to the fourth invention is a rainwater drainage device according to any one of the first to third inventions, in which the size of the gap h is 15 mm or more and 40 mm or less.

A storm water drainage system according to a fifth aspect of the present invention comprises a storm water drainage device according to any one of the first to fourth aspects of the present invention, a water collection pipe connected to the storm water drainage device, and a drain outlet connected to the water collection pipe.

The rainwater drainage device of the present invention effectively generates a siphon effect in the drainage pipe and eliminates factors that inhibit the siphon effect, allowing rainwater to be drained efficiently.

1 is a diagram showing a drainage system including a storm water drainage device according to an embodiment of the present invention. 2A is a cross-sectional view of the rainwater drainage device of FIG. 1, and FIG. 2B is a plan view thereof. FIG. 13 is a diagram showing the results of comparing Examples 1 to 7 of the present invention with Comparative Examples 1 to 4 with respect to the occurrence of vortexes and siphoning. 1A is a side view showing a configuration of a rainwater drainage device according to another embodiment of the present invention, and FIG. 1B is a plan view showing a configuration of a rainwater drainage device according to still another embodiment of the present invention. 1A is a side view showing the configuration of a rainwater drainage device according to still another embodiment of the present invention, and FIG. 1B is a side view showing the configuration of a rainwater drainage device according to still another embodiment of the present invention.

The rainwater drainage device 10 according to one embodiment of the present invention is described below with reference to Figures 1 to 2(b).

As shown in FIG. 1, the rainwater drainage device 10 constitutes part of a rainwater drainage system 50 installed in a building 30.

The building 30 shown in Figure 1 is a three-story building, with slabs 20 provided between the first and second floors and between the second and third floors.

(Rainwater drainage system 50)
As shown in FIG. 1 , the storm water drainage system 50 includes a storm water drainage device 10 , a roof drain 21 (part of a drainage pipe), a water collection pipe 22 , and a drain outlet 23 .

The roof drain 21 is provided to drain rainwater that falls on the flat roof of a structure 30 such as a building into a water collection pipe 22. As shown in FIG. 1, the roof drain 21 is installed in six places along the roof of the structure 30, three on each side.

The roof drain 21 may be, for example, a pipe with an outer diameter of 50A and a circular cross section, and may be connected to the water collection pipe 22 via a pipe with an outer diameter of 65A.

The water collection pipe 22 is provided to collect the rainwater drained from each roof drain 21 and guide it to the drain outlet 23. As shown in FIG. 1, the water collection pipe 22 is arranged on the side of the flat roof of the building 30 so as to incline downward toward the connection side with the drain pipe 14. Furthermore, the water collection pipe 22 is connected to the drain pipe 14 at the downstream end in the direction of movement of the rainwater.

The water collection pipe 22 may be made of a material having a circular or elliptical cross-sectional shape, for example.

As shown in FIG. 1, the drain outlet 23 is connected to the most downstream side of the drain pipe 14, and drains the rainwater collected through the roof drain 21 near the ground.

The drain outlet 23 may be, for example, a pipe with an outer diameter of 100A to 150A and a circular cross section. A pipe with an outer diameter of 100A that is located at the connection with the drain pipe 14 may be combined with a pipe with an outer diameter of 150A that is located at the end on the drain side.

(Rainwater drainage device 10)
As shown in FIG. 1 , the rainwater drainage device 10 is disposed directly above each roof drain 21 .

The material of the rainwater drainage device 10 can be the same as that of the drainage pipe 14, such as olefin resins such as PE (polyethylene) and PP (polypropylene), PVC resin, or metals such as aluminum, aluminum alloy, and stainless steel.

By using resin, aluminum, or aluminum alloy, a rainwater drainage device 10 with the desired shape can be obtained at low cost and with a light weight.

As shown in Figures 2(a) and 2(b), the base portion 11 has a circular bottom surface 11a, a drop outlet 11b for dropping rainwater into the approximate center of the bottom surface 11a, and a cylindrical portion 11c. The cylindrical portion 11c that forms the drop outlet 11b is connected to the upper end of the roof drain 21.

As shown in Figures 2(a) and 2(b), the bottom surface 11a is an annular member with a drop opening 11b formed in the approximate center. A number of flow straightening fins 13 are arranged at equal angular intervals on the annular bottom surface 11a, centered on the drop opening 11b.

As shown in FIG. 2(a), the drop opening 11b is a through hole formed in the center of the base portion 11 and is formed inside the cylindrical portion 11c. The drop opening 11b is connected to the upper end of the roof drain 21, and allows rainwater that flows into the rainwater drainage device 10 from 360 degrees to fall into the roof drain 21.

As shown in Fig. 2(a) and Fig. 2(b), the tubular portion 11c is a cylindrical member, and its upper end is connected to the bottom surface 11a and is formed so as to protrude downward from the bottom surface 11a. The tubular portion 11c has a drop opening 11b formed inside.

As shown in Figs. 2(a) and 2(b), the lid 12 is a circular plate-like member arranged above the base 11 concentrically with the drop opening 11b formed at the center of the base 11, and is supported by a number of flow straightening fins 13 erected on the bottom surface 11a of the base 11. As shown in Fig. 2(a), the lid 12 is arranged above the base 11 (drop opening 11b) with a predetermined gap G (height) h from the bottom surface 11a. Furthermore, the lid 12 is formed so that the circular surface facing the drop opening 11b has a diameter b (the diameter of an imaginary circle inscribed in the surface of the lid 12).

In this embodiment, since the lid portion 12 is a circular plate-shaped member, the diameter b of the inscribed circle of the lid portion 12 corresponds directly to the diameter of the circular lid portion 12.

As shown in Figures 2(a) and 2(b), the multiple flow straightening fins 13 are provided on the bottom surface 11a of the base portion 11 to straighten the flow of rainwater flowing into the drop opening 11b. More specifically, as shown in Figure 2(b), the multiple flow straightening fins 13 are plate-shaped members arranged along a substantially vertical direction, and eight of them are provided at equal angular intervals on the bottom surface 11a around a circle centered on the drop opening 11b.

The eight flow straightening fins 13 are arranged in the radial direction on the annular bottom surface 11a.
As a result, even if rainwater that has flowed into the gap G between the bottom surface 11a of the base portion 11 and the lid portion 12 in a vortex shape (see the dashed line in the figure) as shown in Figure 2 (b), the rainwater can be straightened by the straightening fins 13 and guided toward the center of the drop outlet 11b.

This prevents rainwater from flowing into the roof drain 21 in a vortex shape, which would cause an air column to form in the center.

As a result, the straightening fins 13 prevent an air column from forming in the center of the rainwater flowing into the drop outlet 11b, effectively eliminating the factors that inhibit the siphon phenomenon that occurs within the roof drain 21.

<Relationship between base portion 11 and lid portion 12>
In the rainwater drainage device 10 of this embodiment, in the above-mentioned configuration, when the diameter of the circular lid portion 12 facing the drop outlet 11b of the base portion 11 is b and the size (height) of the specified gap G is h, it is configured to satisfy the following relational expression (1).

6≦b/h≦11 (1)
In this way, the relationship between the diameter b of the lid portion 12 and the size h of the gap G between the bottom surface 11a of the base portion 11 and the lid portion 12 is configured to satisfy relational equation (1), so that the flow rate of rainwater falling from between the bottom surface 11a of the base portion 11 and the lid portion 12 through the drop outlet 11b into the roof drain 21 can be controlled so that it becomes full inside the roof drain 21.

As a result, the siphoning effect can be effectively generated within the roof drain 21, while factors that inhibit the siphoning effect can be eliminated, allowing rainwater to be drained efficiently.

Furthermore, if the inner diameter of the drop opening 11b of the base portion 11 is a, it is configured to satisfy the following relational expression (2).

0.2≦h/a≦0.5 (2)
In this way, the ratio of the inner diameter a of the drop opening 11b to the size h of the gap G between the bottom surface 11a of the base portion 11 and the lid portion 12 is configured to satisfy the relational expression (2), so that the flow rate of rainwater falling from between the bottom surface 11a of the base portion 11 and the lid portion 12 through the drop opening 11b into the roof drain 21 can be stabilized and controlled to maintain a full flow state inside the roof drain 21.

As a result, the siphoning effect can be effectively generated within the roof drain 21, while factors that inhibit the siphoning effect can be eliminated, allowing rainwater to be drained efficiently.

Here, it is preferable that the size (height) h of the predetermined gap G formed between the bottom surface 11a of the base portion 11 and the lid portion 12 described above is set to be within the range of 15 mm or more and 40 mm or less while satisfying the above relational expression (1).

This allows the flow rate of rainwater falling into the roof drain 21 through the drop outlet 11b from between the bottom surface 11a of the base portion 11 and the lid portion 12 to be restricted in the vertical direction, thereby controlling the roof drain 21 to a full flow state.

As a result, the flow rate of rainwater flowing into the roof drain 21 can be more effectively controlled, inducing the occurrence of the siphon phenomenon within the roof drain 21.

Furthermore, it is preferable that the diameter b (diameter of the imaginary circle) of the circular lid portion 12 described above is set to be within the range of 110 mm or more and 155 mm or less while satisfying the above relational expression (1).

This allows the flow rate of rainwater falling into the roof drain 21 through the drop port 11b from between the bottom surface 11a of the base portion 11 and the lid portion 12 to be restricted in the planar direction of the lid portion 12, thereby controlling the flow rate inside the roof drain 21 to a full flow state.

As a result, the flow rate of rainwater flowing into the roof drain 21 can be controlled more effectively, and the occurrence of the siphon phenomenon within the roof drain 21 can be induced.
Comparison of Examples 1 to 4 , Reference Examples 1 to 3, and Comparative Examples 1 to 4
FIG. 3 shows the results of a comparison between Examples 1 to 4 of the present invention, Reference Examples 1, 2, and 3, and Comparative Examples 1 to 4 in terms of whether or not vortexes occur in rainwater as it flows into the roof drain 21, and whether or not siphoning occurs in the roof drain 21.

Reference Example 1

Reference Example 1 shows the results of an experiment in which the inner diameter a of the outlet 11b of the rainwater drainage device 10 was 53.5 mm, the height of the lid portion 12 (the size h of the gap G) was 15 mm, and the diameter b of the lid portion was 150 mm.

In this case, b/h = 10.0, h/a = 0.28, and when the diameter of the roof drain 21 was 50A, no vortex occurred in the rainwater flowing into the roof drain 21 from the outlet 11b. The occurrence of the siphon phenomenon in the roof drain 21 was confirmed.

As a result, according to the rainwater drainage device 10 of Reference Example 1, no vortexes were generated in the rainwater flowing into the roof drain 21, and the rainwater was able to be efficiently drained by the action of the siphon phenomenon.

In Example 1 , the experimental results are shown in which the inner diameter a of the outlet 11b of the rainwater drainage device 10 was 71 mm, the height of the lid portion 12 (the size h of the gap G) was 20 mm, and the diameter b of the lid portion was 190 mm.

In this case, b/h = 9.5, h/a = 0.28, and when the diameter of the roof drain 21 was 75A, no vortex occurred in the rainwater flowing into the roof drain 21 from the outlet 11b. The occurrence of the siphon phenomenon in the roof drain 21 was confirmed.

As a result, according to the rainwater drainage device 10 of the first embodiment, no vortexes are generated in the rainwater flowing into the roof drain 21, and the rainwater can be efficiently drained by the action of the siphon phenomenon.

In Example 2 , the experimental results are shown in which the inner diameter a of the outlet 11b of the rainwater drainage device 10 was 109 mm, the height of the lid portion 12 (the size h of the gap G) was 40 mm, and the diameter b of the lid portion was 300 mm.

In this case, b/h = 7.5, h/a = 0.37, and when the diameter of the roof drain 21 was 100A, no vortex occurred in the rainwater flowing into the roof drain 21 from the outlet 11b. The occurrence of the siphon phenomenon in the roof drain 21 was confirmed.

As a result, according to the rainwater drainage device 10 of the second embodiment, no vortexes are generated in the rainwater flowing into the roof drain 21, and the rainwater can be efficiently drained by the siphon effect.

Reference Example 2

Reference Example 2 shows the results of an experiment in which the inner diameter a of the outlet 11b of the rainwater drainage device 10 was 53.5 mm, the height of the lid portion 12 (the size h of the gap G) was 19 mm, and the diameter b of the lid portion was 150 mm.

In this case, b/h = 7.9, h/a = 0.36, and when the diameter of the roof drain 21 was 50A, no vortex occurred in the rainwater flowing into the roof drain 21 from the outlet 11b. The occurrence of the siphon phenomenon in the roof drain 21 was confirmed.

As a result, according to the rainwater drainage device 10 of Reference Example 2 , no vortexes were generated in the rainwater flowing into the roof drain 21, and the rainwater was able to be efficiently drained by the action of the siphon phenomenon.

Reference Example 3

Reference Example 3 shows the results of an experiment in which the inner diameter a of the outlet 11b of the rainwater drainage device 10 was 68 mm, the height of the lid portion 12 (the size h of the gap G) was 15 mm, and the diameter b of the lid portion was 130 mm.

In this case, b/h = 8.7, h/a = 0.22, and when the diameter of the roof drain 21 was 65A, no vortexes were generated in the rainwater flowing into the roof drain 21 from the outlet 11b. The occurrence of the siphon phenomenon in the roof drain 21 was confirmed.

As a result, according to the rainwater drainage device 10 of Reference Example 3 , no vortexes were generated in the rainwater flowing into the roof drain 21, and the rainwater was able to be efficiently drained by the action of the siphon phenomenon.

In Example 3 , the experimental results are shown in which the inner diameter a of the outlet 11b of the rainwater drainage device 10 was 71 mm, the height of the lid portion 12 (the size h of the gap G) was 25 mm, and the diameter b of the lid portion was 220 mm.

In this case, b/h = 8.8, h/a = 0.35, and when the diameter of the roof drain 21 was 75A, no vortexes were generated in the rainwater flowing into the roof drain 21 from the outlet 11b. The occurrence of the siphon phenomenon in the roof drain 21 was confirmed.

As a result, according to the rainwater drainage device 10 of the third embodiment, no vortexes are generated in the rainwater flowing into the roof drain 21, and the rainwater can be efficiently drained by the action of the siphon phenomenon.

In Example 4 , the experimental results are shown in which the inner diameter a of the outlet 11b of the rainwater drainage device 10 was 109 mm, the height of the lid portion 12 (the size h of the gap G) was 30 mm, and the diameter b of the lid portion was 250 mm.

In this case, b/h = 8.3, h/a = 0.28, and when the diameter of the roof drain 21 was 50A, no vortex occurred in the rainwater flowing into the roof drain 21 from the outlet 11b. The occurrence of the siphon phenomenon in the roof drain 21 was confirmed.

As a result, according to the rainwater drainage device 10 of the fourth embodiment, no vortexes are generated in the rainwater flowing into the roof drain 21, and the rainwater can be efficiently drained by the action of the siphon phenomenon.
(Summary of Examples 1 to 4 )
As described above, according to the configurations of Examples 1 to 4 , in all cases, no vortexes were generated in the rainwater flowing into the roof drain 21, and the rainwater was able to be efficiently drained by the action of the siphon phenomenon.

Comparative Example 1

On the other hand, Comparative Example 1 shows the experimental results in which the inner diameter a of the rainwater drainage device outlet 11b was 53.5 mm, the height of the lid (size h of the gap G) was 15 mm, and the diameter b of the lid was 60 mm.

In this case, when b/h = 4.0, h/a = 0.28, and the roof drain diameter was 50A, vortexes were observed in the rainwater flowing into the roof drain from the outlet. And no siphoning occurred in the drain pipe.

In other words, in Comparative Example 1, among the parameters, b/h and h are outside the ranges specified in the above embodiment.

As a result, with the rainwater drainage device of Comparative Example 1, vortices were generated in the rainwater flowing into the roof drain, and the siphon effect could not be generated, making it impossible to drain the rainwater efficiently.

Here, when comparing Comparative Example 1 with a comparative example similar to this configuration, it is found that the diameter b of the lid portion is different.

Therefore, with regard to b/h, although favorable results were obtained at 10.0 in Comparative Example 1, favorable results were not obtained at 4.0 in Comparative Example 1 which did not satisfy the above relational expression (1).

In addition, while favorable results were obtained when the diameter b of the lid was 150 mm in Comparative Example 1, favorable results were not obtained when the diameter b of the lid was 60 mm in Comparative Example 1, as the lid was too small to stabilize the amount of rainwater inflow.

Comparative Example 2

Comparative Example 2 shows the experimental results for the following settings: inner diameter a of the rainwater drainage device outlet = 53.5 mm, height of the lid (size of gap G h) = 50 mm, and diameter b of the lid = 250 mm.

In this case, b/h = 5.0, h/a = 0.93, and when the roof drain had a diameter of 50A, vortexes were observed in the rainwater flowing into the roof drain from the outlet. And no siphoning occurred in the roof drain.

In other words, in Comparative Example 2, among the parameters, b/h, h/a, h, and b are all outside the ranges specified in the above embodiment.

As a result, with the rainwater drainage device of Comparative Example 2, vortices were generated in the rainwater flowing into the roof drain, and the siphon effect could not be generated, making it impossible to drain the rainwater efficiently.

Comparative Example 3

Comparative Example 3 shows the experimental results for the following settings: inner diameter a of the rainwater drainage device outlet = 53.5 mm, height of the lid (size h of the gap G) = 15 mm, and diameter b of the lid = 190 mm.

In this case, b/h = 12.7, h/a = 0.28, and when the roof drain had a diameter of 50A, no vortexes were observed in the rainwater flowing into the roof drain from the outlet, but no siphoning occurred in the roof drain.

In other words, in Comparative Example 3, among the parameters, b/h and b are outside the ranges specified in the above embodiment.

As a result, with the rainwater drainage device of Comparative Example 3, although no vortexes were generated in the rainwater flowing into the roof drain, the siphon effect could not be generated, and therefore the rainwater could not be drained efficiently.

Comparative Example 4

Comparative Example 4 shows the experimental results for the following settings: inner diameter a of the rainwater drainage device outlet = 71 mm, height of the lid (size h of the gap G) = 45 mm, and diameter b of the lid = 190 mm.

In this case, b/h = 4.2, h/a = 0.63, and when the roof drain diameter was 75A, vortexes were observed in the rainwater flowing into the roof drain from the outlet. And no siphoning occurred in the roof drain.

In other words, in Comparative Example 4, among the parameters, b/h, h/a, h, and b are all outside the ranges specified in the above embodiment.

As a result, with the rainwater drainage device of Comparative Example 4, vortices were generated in the rainwater flowing into the roof drain, and the siphon effect could not be generated, making it impossible to drain the rainwater efficiently.

When comparing Comparative Example 4 with Example 1 which has a similar configuration, it is found that h is different.

Therefore, with regard to b/h, while favorable results were obtained at 9.5 in Example 1 , at 4.2 in Comparative Example 4, the position of the lid was too high and the amount of rainwater inflow could not be stabilized, and favorable results were not obtained.

As for h/a, while a favorable result was obtained at 0.28 in Example 1 , a favorable result was not obtained at 0.63 in Comparative Example 4.

Furthermore, while the size h of the gap G of 20 mm in Example 1 provided favorable results, the size h of the gap G of 45 mm in Comparative Example 4 did not provide favorable results.
(summary)
(About b/h)
As a result of the above Examples 1 to 4 , it was found that if the ratio b/h of the diameter b of the lid portion 12 to the height of the lid portion 12 (the size h of the gap G) was 7.5 or more and 10.0 or less, a siphon effect could be generated without generating a vortex within the roof drain 21.

On the other hand, the results of Comparative Examples 1 to 4 above show that when b/h is less than 5.0 or greater than 12.7, vortexes form within the roof drain 21, and the siphon effect cannot be generated, making it difficult to drain rainwater efficiently.

Therefore, as explained in the above embodiment, it is preferable that b/h is set to satisfy the following relational expression (1):

7.5≦b/h≦10.0 (1)
(Regarding h / a)
Next, as a result of the above Examples 1 to 4 , if the ratio h/a of the inner diameter a of the drop outlet 11b to the height of the lid portion 12 (the size h of the gap G) is 0.22 or more and 0.37 or less, a siphon effect can be generated without generating a vortex in the drain pipe 14.

On the other hand, the results of Comparative Examples 1 to 4 above show that when h/a is below 0.28 or above 0.63, vortexes are generated in the drain pipe 14, and the siphon effect cannot be generated, making it difficult to drain rainwater efficiently.

Therefore, as explained in the above embodiment, it is preferable that h/a is set to satisfy the following relational expression (2).

0.22≦h/a≦0.37 (2)
(Regarding the size h of the gap G)
Next, as a result of the above Examples 1 to 4 , when the size h of the gap G was 15 mm or more and 40 mm or less, no vortex was generated within the roof drain 21 and the siphon phenomenon was able to occur.

On the other hand, the results of the above Comparative Examples 1 to 4 show that when the size h of the gap G is less than 15 mm or more than 45 mm, vortexes are generated within the roof drain 21, and the siphon effect cannot be generated, making it impossible to drain rainwater efficiently.

Therefore, as explained in the above embodiment, it is preferable that the size h of the gap G be set in the range of 15 mm or more and 40 mm or less.

(For diameter b)
Furthermore, the results of the above Examples 1 to 4 show that if the diameter b of the lid portion 12 is 130 mm or more and 300 mm or less, a vortex is not generated in the drain pipe 14 and a siphon effect can be generated.

On the other hand, the results of the above Comparative Examples 1 to 4 show that when the diameter b of the lid portion 12 is less than 60 mm or more than 190 mm, vortexes are generated in the drain pipe 14, and the siphon effect cannot be generated, making it difficult to drain rainwater efficiently.

Therefore, as explained in the above embodiment, it is preferable that the diameter b of the lid portion 12 is set in the range of 130 mm or more and 300 mm or less.

[Other embodiments]
Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications are possible without departing from the gist of the invention.

(A)
In the above embodiment, an example has been described in which a plurality of flow straightening fins 13 are provided radially along the outer periphery of the bottom surface 11a of the base portion 11 of the rainwater drainage device 10. However, the present invention is not limited to this.

For example, as shown in FIG. 4(a), the rainwater drainage device 110 may have no flow straightening fins on the bottom surface 11a of the base portion 11.

Even in this case, by stabilizing the amount of rainwater flowing into the roof drain, the siphon effect can be effectively generated inside the roof drain, resulting in the same effect as above.

(B)
In the above embodiment, an example has been described in which eight flow straightening fins 13 are provided radially along the outer periphery of the bottom surface 11a of the base portion 11 of the rainwater drainage device 10. However, the present invention is not limited to this.

For example, as shown in FIG. 4(b), the rainwater drainage device 210 may have half the number of flow straightening fins 13, that is, four.

That is, the number of flow straightening fins is not particularly limited and may be any number.
Furthermore, the straightening fins are not limited to being arranged radially along the radial direction of a circle centered on the drop opening 11b of the base portion 11, but may be arranged at an angle to the radial direction.

(C)
In the above embodiment, an example has been described in which a smooth plate-shaped member is used as the lid portion 12. However, the present invention is not limited to this.

For example, as shown in FIG. 5(a), the rainwater drainage device 310 may include a cover portion 312 having a concave surface facing the drop opening 11b.

Alternatively, as shown in FIG. 5(b), the rainwater drainage device 410 may include a cover portion 412 having a concave surface formed on the side opposite to the surface facing the drop opening 11b.

In addition, in the configurations of these rainwater drainage devices 310 and 410, the size (height) h of the gap G used in the above equation may be set using the height that results in the smallest gap between the surface facing the drop outlet 11b and the bottom surface 11a.

(D)
In the above embodiment, an example has been described in which the cover 12 is configured from a circular plate-shaped member, but the present invention is not limited to this.

For example, the shape of the lid is not limited to a circle, but may be other shapes such as an ellipse or a polygon.
In addition, when the lid portion has a shape other than a circle, it is sufficient that the above relational expression is satisfied, with b being the diameter of a circle inscribed on the surface of the lid portion facing the drop opening.

However, in order to distribute the rainwater flowing into the outlet evenly around the entire circumference, it is preferable to use a circular lid as in the above embodiment.

(E)
In the above embodiment, an example has been described in which the rainwater drainage device 10 is installed inside the water collection pipe 22 arranged along a substantially horizontal direction near the lower end of the roof R. However, the present invention is not limited to this.

For example, the rainwater drainage device of the present invention may be installed on the roof or at the edge of a flat roof.

The rainwater drainage device of the present invention effectively generates a siphon effect in the drainage pipe, and eliminates factors that inhibit the generation of the siphon effect, allowing rainwater to be drained efficiently, making it widely applicable to various drainage systems that utilize the siphon effect.

10 Rainwater drainage device 11 Base portion 11a Bottom surface 11b Drop opening 11c Cylindrical portion 12 Lid portion 13 Flow straightening fin 14 Drain pipe 20 Slab 21 Roof drain 22 Water collection pipe 23 Drain opening 30 Building 50 Rainwater drainage system 110 Rainwater drainage device 210 Rainwater drainage device 310 Rainwater drainage device 312 Lid portion 410 Rainwater drainage device 412 Lid portion a Inner diameter b Diameter h Gap size G Gap R Roof

Claims (5)

A rainwater drainage device that collects rainwater and drains it from a drain pipe,
A base portion having a bottom surface and a drop outlet connected to the drain pipe;
A lid portion facing the drop opening and disposed at a predetermined gap from the bottom surface;
Equipped with
If the size of the gap is h and the inner diameter of the drop hole is a, the following relational expression (1) is satisfied:
The size of the gap h is 20 mm or more and 40 mm or less ,
The diameter b of the lid portion is 190 mm or more and 300 mm or less.
Storm water drainage system.
0.22≦h/a≦0.37 (1) A plurality of fins are disposed on the outer periphery of the bottom surface of the base portion and are disposed at equal angular intervals around the drop opening.
The rainwater drainage system according to claim 1. The lid portion is disposed along a radial direction of a virtual circle inscribed on the surface of the lid portion.
The outer peripheral end of the fin protrudes from the outer edge of the lid.
A rainwater drainage system according to claim 2 . The lid portion is a circular plate.
A rainwater drainage device according to any one of claims 1 to 3. A rainwater drainage device according to any one of claims 1 to 4,
A water collection pipe connected to the rainwater drainage device;
A drainage outlet connected to the water collection pipe;
A storm water drainage system that includes:

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