Backflow prevention tank

Abstract

To provide a backflow prevention basin that prevents intrusion of drainage flowing back through a drainage pipeline to an upstream side, while suppressing occurrence of drainage clogging due to filth even when an amount of the drainage is small.SOLUTION: A backflow prevention basin 10 is provided in the drainage pipeline connecting an indoor drainage facility and a sewer pipe. The backflow prevention basin 10 comprises: a catch basin body 11; an inflow pipe part 12 and an outflow pipe part 13 for drainage provided on a side wall of the catch basin body 11; and a backflow prevention valve 14 provided in the catch basin body 11. The backflow prevention valve 14 has a valve body 141 configured to be able to close a downstream opening 12b of the inflow pipe part 12. A downstream side pipe bottom of the inflow pipe part 12 is located below an upstream side pipe bottom of the inflow pipe part 12.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a backflow prevention manhole that is installed in a drainage pipe connecting indoor drainage equipment such as a toilet to a sewer pipe, and that prevents wastewater flowing backward through the drainage pipe from entering the upstream side. [Background technology]

[0002] Generally, wastewater discharged from indoor drainage facilities such as toilets is discharged into the main sewer pipe (hereinafter simply referred to as the sewer pipe) via drainage pipes buried underground. In addition, a drainage manhole is usually installed upstream of the connection point between the drainage pipe and the sewer pipe in order to remove and inspect waste such as garbage in the drainage pipe.

[0003] However, when a large amount of rainwater flows into a sewer pipe in a short period of time due to a typhoon or other event, the overflowing wastewater exceeds the drainage capacity of the sewer pipe and flows back up the drainage pipe through the drainage manhole, causing problems such as the backflowing wastewater spraying into the building from the indoor drainage equipment connected to the drainage pipe, or the air compressed by the wastewater causing seal water to spray into the building.

[0004] In response to this, in order to prevent wastewater that has backflowed from the sewer pipes from passing through the drainage manhole and spraying out of the indoor drainage equipment, Patent Document 1 discloses a backflow prevention manhole that has a backflow prevention valve attached to the inlet opening inside the drainage manhole.

[0005] In the backflow prevention tank described in Patent Document 1, the valve element of the backflow prevention valve is rotatably attached to the inlet opening so that it inclines from upstream to downstream as it moves from top to bottom. Therefore, the valve element of the backflow prevention valve normally closes the inlet opening due to its own weight. As a result, when wastewater flows from the indoor drainage system into the drainage tank, the valve element is lifted by the flow of wastewater, opening the inlet opening. On the other hand, when wastewater backflows from the sewer pipe into the drainage tank, the valve element closes the inlet opening due to its own weight and the flow of wastewater, preventing the wastewater from backflowing through the drainage tank into the upstream drainage pipe. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-126888 Summary of the Invention [Problem to be solved by the invention]

[0007] With the recent spread of water-saving toilets, the normal amount of water discharged from indoor drainage systems has been greatly reduced. However, in the case of the backflow prevention manhole described in Patent Document 1, the valve body normally blocks the inlet opening of the drainage manhole due to its own weight, so when the amount of water discharged decreases, the valve body becomes difficult to open, causing waste such as garbage to accumulate around the valve body and clog the flow.

[0008] In view of the above, the present disclosure aims to provide a backflow prevention manhole that prevents wastewater from flowing backward through a drainage pipe from entering the upstream side, so that drainage blockages caused by filth and the like can be prevented even when the amount of drainage is small. [Means for solving the problem]

[0009] In order to achieve the above-mentioned object, a first aspect of the present disclosure is a backflow prevention manhole that is installed in a drainage pipeline connecting an indoor drainage system and a sewer pipe and prevents wastewater that flows backward through the drainage pipeline from entering the upstream side, and that comprises a drainage manhole body, inlet and outlet pipe sections for wastewater installed on the side wall of the drainage manhole body, and a backflow prevention valve installed within the drainage manhole body and having a valve body configured to be able to close the downstream opening of the inlet pipe section, and the downstream pipe bottom of the inlet pipe section is located lower than the upstream pipe bottom of the inlet pipe section.

[0010] According to the first aspect, the downstream bottom of the wastewater inlet pipe, which is installed on the side wall of the drainage manhole body, is located lower than the upstream bottom. This increases the flow rate of the wastewater as it flows from the upstream side to the downstream side of the inlet pipe, making it easier for the valve element of the check valve that blocks the downstream opening of the inlet pipe to open. Therefore, even when the amount of wastewater is small, clogging of the backflow prevention manhole with wastewater or other debris can be prevented.

[0011] A second aspect of the present disclosure is a backflow prevention tank in which, in the first aspect, the bottom of the drainage tank body is located below the downstream pipe bottom of the inlet pipe section.

[0012] According to the second aspect, it is possible to avoid a situation in which waste matter or the like accumulates downstream of the valve body of the check valve within the drainage manhole body, thereby preventing the valve body from opening, thereby further preventing drainage blockages caused by waste matter or the like.

[0013] A third aspect of the present disclosure is a backflow prevention tank according to the first or second aspect, wherein the difference in elevation between the downstream pipe bottom and the upstream pipe bottom in the inlet pipe section is 23% or more of the inner diameter of the piping connected to the inlet pipe section from the upstream side.

[0014] According to the third aspect, the flow rate of the wastewater can be sufficiently increased as it flows from the upstream side to the downstream side of the inlet pipe, which makes it easier for the valve element of the check valve to open due to the flow of wastewater, thereby further preventing the drain from becoming clogged with waste matter.

[0015] A fourth aspect of the present disclosure is a backflow prevention tank, which is any one of the first to third aspects, wherein the inlet pipe section includes at least a valve pipe attached to the downstream side from the inside of the drainage tank body, and a valve seat surface that can abut against the valve body is provided on the downstream end face of the valve pipe.

[0016] According to the fourth aspect, the valve pipe that is opened and closed by the valve body is attached from the inside of the drainage manhole body, so that the valve body can be attached integrally with the valve pipe, making it easier to assemble the backflow prevention manhole.

[0017] A fifth aspect of the present disclosure is a backflow prevention mass in any one of the first to fourth aspects, wherein the inlet pipe section includes at least a first horizontal pipe section arranged upstream and having a horizontal or approximately horizontal pipe bottom, and an inclined pipe section arranged downstream of the first horizontal pipe section and having a pipe bottom that slopes downward toward the downstream side.

[0018] According to the fifth aspect, even when the flow gradient of the pipe connected from the upstream side to the inlet pipe section of the backflow prevention mass is small, the pipe can be easily connected to the first horizontal pipe section of the inlet pipe section.

[0019] A sixth aspect of the present disclosure is a backflow prevention tank in the fifth aspect, wherein the first horizontal pipe section and the inclined pipe section are integrally molded, the inlet pipe section is inserted into the drainage tank body, and a valve seat surface that can abut against the valve body is provided on the downstream end face of the inlet pipe section.

[0020] According to the sixth aspect, the number of components of the backflow prevention mass can be reduced, making it easier to assemble the backflow prevention mass.

[0021] A seventh aspect of the present disclosure is a backflow prevention manhole in the fifth or sixth aspect, wherein the inlet pipe section is arranged downstream of the inclined pipe section, is connected to the drainage manhole body, and further includes a second horizontal pipe section whose pipe bottom is horizontal or approximately horizontal.

[0022] According to the seventh aspect, the second horizontal pipe section of the inlet pipe section can be easily attached to the side wall of the drainage basin body.

[0023] An eighth aspect of the present disclosure is a backflow prevention mass in any one of the fifth to seventh aspects, wherein an extension line of the pipe axis of the first horizontal pipe section passes through the downstream opening of the inlet pipe section without intersecting the inner wall surface of the inclined pipe section.

[0024] According to the eighth aspect, it is possible to avoid a situation in which the wastewater flow rate decreases due to collision with the top of the inclined pipe section when flowing from the upstream side to the downstream side of the inlet pipe section, thereby making it possible to make the valve body of the check valve more likely to open due to the flow of wastewater.

[0025] A ninth aspect of the present disclosure is a backflow prevention mass in any one of the first to eighth aspects, wherein the downstream side of the inlet pipe section is inserted into the inside of the drainage mass body, the valve body vertically blocks the downstream opening of the inlet pipe section when no drainage is occurring, and a valve seat surface is provided on the periphery of the downstream opening of the inlet pipe section so as to be able to abut against the valve body when drainage backflows.

[0026] According to the ninth aspect, the structure of the inlet pipe section is simplified, making it easier to assemble the backflow prevention mass. It also makes it easier to open and close the valve body when discharging water, and prevents air from being forced upstream when backflow of wastewater occurs, thereby preventing seal failure in the drainage pipe.

[0027] A tenth aspect of the present disclosure is a backflow prevention mass according to the ninth aspect, wherein the valve seat surface is provided in a shape that widens in the downstream direction from the inner circumferential surface to the end face of the inlet pipe portion.

[0028] According to the tenth aspect, when backflow of wastewater occurs, the water blocking effect of the valve body can be reliably obtained even with a weaker force (water pressure). [Effects of the Invention]

[0029] According to the present disclosure, a backflow prevention manhole that prevents wastewater flowing backward through a drainage pipe from entering the upstream side can prevent drainage blockages caused by filth and the like even when the amount of wastewater is small. [Brief explanation of the drawings]

[0030] [Figure 1] FIG. 1 is a diagram showing an example of a drainage pipeline in which a backflow prevention block according to an embodiment is provided. [Figure 2]FIG. 2 is a vertical cross-sectional view of the backflow prevention tank according to the embodiment. [Figure 3] 3 is a cross-sectional view schematically showing the connection point between the drainage manhole body and the inflow pipe section in the backflow prevention manhole shown in FIG. 2 and the vicinity thereof. [Figure 4] Figure 4 is a cross-sectional view showing the difference in elevation between the downstream pipe bottom and the upstream pipe bottom of the inlet pipe section in a backflow prevention manhole of the embodiment, and the difference in elevation between the bottom of the drainage manhole body and the downstream pipe bottom of the inlet pipe section. [Figure 5] FIG. 5 is a vertical cross-sectional view of a backflow prevention mass according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0031] (Embodiment) A backflow prevention mass according to an embodiment of the present disclosure will be described in detail below with reference to the drawings. Note that the present disclosure is not limited to the following embodiment, and various modifications are possible within the scope of the technical concept of the present disclosure.

[0032] <Example of drainage pipe configuration> As shown in FIG. 1, for example, the backflow prevention manhole 10 of this embodiment is provided in a drainage pipeline 1 that connects an indoor drainage system 2, such as a toilet, to a sewer pipe (not shown), and prevents wastewater flowing backward through the drainage pipeline 1 from entering the upstream side. Other drainage manholes 3A, 3B, and 3C, for example, may be provided between the indoor drainage system 2 and the backflow prevention manhole 10 in the drainage pipeline 1 to allow for the removal and inspection of waste such as garbage in the drainage pipeline 1. The piping that constitutes the drainage pipeline 1 is, for example, a polyvinyl chloride pipe VU100 with an inner diameter of 107 mm, and the piping may be provided with a flow gradient of, for example, about 1 / 200 toward the downstream side.

[0033] <Example of backflow prevention tank configuration> 2 and 3, the backflow prevention manhole 10 includes a drainage manhole body 11, a drainage inlet pipe section 12 and an outlet pipe section 13 provided on the side wall of the drainage manhole body 11, and a backflow prevention valve 14 provided within the drainage manhole body 11. The backflow prevention manhole 10 may be made of a synthetic resin such as polyvinyl chloride.

[0034] An opening 11a is provided at the top of the drainage manhole body 11 for inserting a height adjustment adjuster or a lid (not shown). The opening 11a has a circular shape with a diameter of, for example, about 50 to 300 mm. By inserting the adjuster or lid into the opening 11a, the backflow prevention manhole 10 can be exposed to the ground surface, allowing inspection and maintenance of the backflow prevention manhole 10.

[0035] An opening 11b is provided in the side wall of the drainage manhole body 11, and the downstream side of the inflow pipe section 12 is inserted into the inside of the drainage manhole body 11 through this opening 11b, thereby connecting the drainage manhole body 11 and the inflow pipe section 12. That is, in this embodiment, the drainage manhole body 11 and the inflow pipe section 12 are configured as separate bodies, and the inflow pipe section 12 is inserted from the outside of the drainage manhole body 11 toward the inside.

[0036] The inflow pipe section 12 includes a first horizontal pipe section 121 located upstream, an inclined pipe section 122 located downstream of the horizontal pipe section 121, and a second horizontal pipe section 123 located downstream of the inclined pipe section 122. The first horizontal pipe section 121, the inclined pipe section 122, and the second horizontal pipe section 123 may be integrally molded. The pipe bottoms (bottoms of the pipe inner walls) of the first horizontal pipe section 121 and the second horizontal pipe section 123 are horizontal or approximately horizontal. The pipe bottom of the inclined pipe section 122 is inclined downward toward the downstream side. Therefore, the pipe bottoms of the inclined pipe section 122 and the second horizontal pipe section 123 are located lower than the pipe bottom of the first horizontal pipe section 121. In other words, the pipe bottom on the downstream side of the inflow pipe section 12 is located lower than the pipe bottom on the upstream side of the inflow pipe section 12.

[0037] Although not shown, the upstream opening 12a of the inlet pipe section 12 (first horizontal pipe section 121) is connected to a pipe (upstream pipe on the indoor drainage system 2 side) that constitutes the drainage pipeline 1. Specifically, the outer diameter of the upstream pipe is approximately equal to the inner diameter of the first horizontal pipe section 121, and the downstream end of the upstream pipe is inserted into the first horizontal pipe section 121. A step 121a is provided along the inner circumference of the first horizontal pipe section 121 at the boundary with the inclined pipe section 122. The inner peripheral surface of the inclined pipe section 122 may have a curved surface that bulges outward when viewed from the pipe axis of the inclined pipe section 122. This curved surface can smooth the flow of drainage water. The inner diameters of the inclined pipe section 122 and the second horizontal pipe section 123 may be approximately equal to the inner diameter of the upstream pipe inserted into the first horizontal pipe section 121. The tip of the upstream pipe inserted into the first horizontal pipe section 121 abuts against the step 121a, thereby positioning the upstream pipe in the insertion direction.

[0038] The outer diameter of the second horizontal pipe section 123 is approximately equal to the diameter of the opening 11b of the drainage manhole body 11, and the second horizontal pipe section 123 is inserted into the drainage manhole body 11 through the opening 11b. That is, the downstream opening 12b of the inlet pipe section 12 (second horizontal pipe section 123) is located closer to the interior of the drainage manhole body 11 than the opening 11b of the drainage manhole body 11. A protrusion 123a is provided along the outer periphery of the second horizontal pipe section 123 at the boundary with the inclined pipe section 122. When the second horizontal pipe section 123 is inserted into the drainage manhole body 11, the protrusion 123a of the second horizontal pipe section 123 abuts against the side wall around the opening 11b of the drainage manhole body 11, thereby positioning the second horizontal pipe section 123 in the insertion direction.

[0039] The sidewall around the opening 11b of the drainage manhole body 11 may be provided with a protruding portion 11c that protrudes outward from the drainage manhole body 11. In this case, the protruding portion 11c of the drainage manhole body 11 may be arranged cylindrically to surround the opening 11b, and the tip surface of the protruding portion 11c may be made flush with a flat surface. In this way, the tip surface of the protruding portion 11c of the drainage manhole body 11 can be in surface contact with the side surface (downstream side) of the protruding portion 123a of the second horizontal pipe section 123, thereby enabling a good connection between the inlet pipe section 12 and the drainage manhole body 11 without using a packing or the like.

[0040] In this embodiment, to facilitate the flow of wastewater downstream after passing through the downstream opening 12b of the second horizontal pipe section 123, the bottom of the drainage manhole body 11 may be positioned further below the bottom of the second horizontal pipe section 123, i.e., the bottom of the downstream pipe of the inlet pipe section 12. In this case, the drainage manhole body 11 may be provided with an inclined section that slopes downward downstream from the lower end of the downstream opening 12b of the second horizontal pipe section 123 to the bottom of the drainage manhole body 11. The drainage manhole body 11 may also be provided with a horizontal section that connects to the inclined section and supports the second horizontal pipe section 123, and a support section that supports the horizontal section and is positioned below the opening 11b of the drainage manhole body 11.

[0041] The inclination of the inclined pipe section 122 may be set so that the difference in height between the bottom of the first horizontal pipe section 121 and the bottom of the second horizontal pipe section 123 is 23% or more of the inner diameter of the upstream piping (the piping connected to the inflow pipe section 12 from the upstream side). Also, the inclination of the inclined pipe section 122 may be set so that the extension line (dashed line in FIG. 2) of the pipe axis (center axis) of the first horizontal pipe section 121 passes through the downstream opening 12b of the inflow pipe section 12 without intersecting the inner wall surface of the inclined pipe section 122. In other words, the difference in height between the bottom of the first horizontal pipe section 121 and the bottom of the second horizontal pipe section 123 may be set to less than 50% of the inner diameter of the inclined pipe section 122 (the inner diameter of the upstream piping).

[0042] The outflow pipe section 13 may be integrally molded with the drainage manhole main body 11. The bottom of the drainage manhole main body 11 and the bottom of the outflow pipe section 13 may be located at approximately the same height. Although not shown, a pipe (the downstream pipe on the sewer pipe side) that constitutes the drainage pipeline 1 is connected to the opening (downstream opening) of the outflow pipe section 13. Specifically, the outer diameter of the downstream pipe is approximately equal to the inner diameter of the opening side of the outflow pipe section 13, and the upstream end of the downstream pipe is inserted into the outflow pipe section 13. A step 13a is provided along the inner circumference of the outflow pipe section 13, and the inner diameter of the outflow pipe section 13 upstream of the step 13a is smaller than the inner diameter of the opening side of the outflow pipe section 13, i.e., the outer diameter of the downstream pipe. As a result, the tip of the downstream pipe inserted into the outflow pipe section 13 abuts against the step 13a, thereby positioning the downstream pipe in the insertion direction.

[0043] The check valve 14 has a substantially disk-shaped valve element 141 configured to close the downstream opening 12b of the inlet pipe section 12. The check valve 14 further has a support section 142 that rotatably supports the valve element 141, a rotary shaft 143 provided on the support section 142 opposite the valve element 141, and a bearing member 15 that supports the rotary shaft 143. An extension section 111 extending toward the interior of the drainage manhole body 11 along the outer periphery of the second horizontal pipe section 123 is provided above the opening 11b on the inner wall of the drainage manhole body 11. The bearing member 15 is fixed to the extension section 111 by adhesive, screwing, welding, or other methods. The bearing member 15 may also be removably fixed by being fitted into the extension section 111, for example. Making the bearing member 15 removable allows it to be easily replaced if damaged. The rotation shaft 143 supported by the bearing member 15 is disposed upstream of the center of gravity of the valve body 141. The extension portion 111 may be integrally formed with the drainage basin main body 11.

[0044] The opening surface of the downstream opening 12b of the inlet pipe section 12 (second horizontal pipe section 123) is substantially vertical, and the valve element 141 blocks the downstream opening 12b substantially perpendicularly along this vertical surface when no drainage is occurring. That is, the angle that the disc shape of the valve element 141 makes with the vertical plane when closing the downstream opening 12b is substantially 0°. A valve seat surface 12c that can abut against the valve element 141 is provided on the downstream end surface of the inlet pipe section 12, i.e., on the periphery of the downstream opening 12b of the inlet pipe section 12. The valve seat surface 12c is configured to be able to abut against the valve element 141 when drainage backflows. The valve seat surface 12c may be provided in a shape that diverges downstream from the inner circumferential surface to the end surface of the inlet pipe section 12 (second horizontal pipe section 123). That is, the valve seat surface 12c may be a tapered surface (inclined surface). An annular packing 16 capable of coming into close contact with the valve seat surface 12c of the inlet pipe portion 12 is provided on the outer circumferential surface of the valve body 141.

[0045] In this embodiment, an inverted portion 11d having, for example, a semicircular cross section may be provided at the bottom of the drainage manhole main body 11. The bottom of the inverted portion 11d and the bottom of the outflow pipe portion 13 may be located at approximately the same height. The inverted portion 11d may be provided extending from the bottom of the drainage manhole main body 11 to the downstream opening 12b of the second horizontal pipe portion 123. In this way, the inverted portion 11d connects the inflow pipe portion 12 and the outflow pipe portion 13, thereby preventing sewage and the like from accumulating during drainage.

[0046] <Example of backflow prevention block operation> When no drainage is occurring, the valve element 141 of the check valve 14 contacts the valve seat surface 12c of the inlet pipe section 12, blocking the downstream opening 12b of the inlet pipe section 12. When the valve element 141 is blocking the downstream opening 12b and wastewater flows out of the indoor drainage equipment 2, the wastewater that flows into the inlet pipe section 12 through the drainage pipe line 1 pushes open the valve element 141, which is in contact with the valve seat surface 12c of the inlet pipe section 12, by water pressure. As a result, the wastewater flows from the inlet pipe section 12 into the drainage manhole body 11, and then flows through the outflow pipe section 13 and out of the backflow prevention manhole 10. Furthermore, because the center of gravity of the valve element 141 is located downstream of the rotation axis 143, once the wastewater has flowed out of the inlet pipe section 12, the valve element 141 closes the downstream opening 12b again due to its own weight.

[0047] On the other hand, even if the wastewater exceeds the drainage capacity of the sewer pipe due to heavy rain or the like and overflows, flowing back up the drainage pipeline 1, the downstream opening 12b of the inlet pipe section 12 is closed by the valve body 141 of the check valve 14, so the wastewater will not enter the drainage pipeline 1 upstream of the check valve 14. Therefore, it is possible to prevent the backflowing wastewater and the air compressed by this wastewater from spraying out of the indoor drainage equipment 2.

[0048] <Effects of the embodiment> In the backflow prevention manhole 10 of this embodiment described above, the downstream pipe bottom of the wastewater inlet pipe 12 provided on the side wall of the drainage manhole body 11 is located lower than the upstream pipe bottom. Therefore, the flow rate of the wastewater increases when the wastewater flows from the upstream side to the downstream side of the inlet pipe 12, making it easier for the valve element 141 of the backflow prevention valve 14 that blocks the downstream opening 12b of the inlet pipe 12 to open due to the flow of wastewater. Therefore, even when the amount of wastewater is small, clogging of the backflow prevention manhole 10 by wastewater or the like can be suppressed. The backflow prevention manhole 10 of this embodiment is particularly useful when the flow gradient of the pipe connected from the upstream side to the inlet pipe 12 is small and the flow rate of the wastewater in that pipe is slow.

[0049] Furthermore, in the backflow prevention manhole 10 of this embodiment, the bottom of the drainage manhole body 11 may be located lower than the bottom of the downstream pipe of the inlet pipe section 12. This prevents waste matter from accumulating downstream of the valve body 141 of the backflow prevention valve 14 inside the drainage manhole body 11 and obstructing the opening of the valve body 141. This further prevents drainage blockages in the backflow prevention manhole 10 due to waste matter.

[0050] Furthermore, in the backflow prevention manhole 10 of this embodiment, the height difference between the bottom of the downstream side and the bottom of the upstream side of the inflow pipe section 12 may be 23% or more of the inner diameter of the pipe connected to the inflow pipe section 12 from the upstream side. This sufficiently increases the flow rate of the wastewater as it flows from the upstream side to the downstream side of the inflow pipe section 12, making it easier for the valve body 141 of the backflow prevention valve 14 to open due to the flow of wastewater. This further reduces the occurrence of wastewater clogging in the backflow prevention manhole 10 due to sewage and the like.

[0051] Furthermore, in the backflow prevention tank 10 of this embodiment, the inflow pipe section 12 may include a first horizontal pipe section 121 that is located upstream and has a horizontal or approximately horizontal pipe bottom, and an inclined pipe section 122 that is located downstream of the first horizontal pipe section 121 and has a pipe bottom that is inclined downward toward the downstream side. In this way, the piping that is connected to the inflow pipe section 12 from the upstream side can be easily connected to the first horizontal pipe section 121 of the inflow pipe section 12.

[0052] Furthermore, in the backflow prevention manhole 10 of this embodiment, the inflow pipe section 12 may further include a second horizontal pipe section 123 that is located downstream of the inclined pipe section 122, is connected to the drainage manhole body 11, and has a horizontal or approximately horizontal pipe bottom. In this way, the second horizontal pipe section 123 of the inflow pipe section 12 can be easily attached to the side wall of the drainage manhole body 11.

[0053] Furthermore, in the backflow prevention block 10 of this embodiment, the extension of the pipe axis of the first horizontal pipe section 121 may pass through the downstream opening 12b of the inlet pipe section 12 without intersecting the inner wall surface of the inclined pipe section 122. This prevents the wastewater from colliding with the pipe apex (the apex of the pipe inner wall) of the inclined pipe section 122 when flowing from the upstream side to the downstream side of the inlet pipe section 12, thereby preventing the flow rate of the wastewater from decreasing. This makes it possible to realize a state in which the valve body 141 of the backflow prevention valve 14 is easily opened by the flow of wastewater.

[0054] In the backflow prevention tank 10 of this embodiment, the first horizontal pipe section 121, the inclined pipe section 122, and the second horizontal pipe section 123 may be integrally molded. This reduces the number of components of the backflow prevention tank 10, making it easier to assemble the backflow prevention tank 10.

[0055] Furthermore, in the backflow prevention manhole 10 of this embodiment, the downstream side of the inlet pipe section 12 may be inserted into the drainage manhole body 11. This simplifies the configuration of the inlet pipe section 12, making it easier to assemble the backflow prevention manhole 11. Specifically, if the downstream end of the inlet pipe section 12 were to be in direct contact with the cylindrical side wall of the drainage manhole body 11 without being inserted into the drainage manhole body 11, the connection portion of the inlet pipe section 12 with the drainage manhole body 11 would have to be formed into a complex shape. In contrast, in this embodiment, as described above, the inlet pipe section 12 and the drainage manhole body 11 can be satisfactorily connected without using a packing or the like.

[0056] Furthermore, in the backflow prevention block 10 of this embodiment, the valve element 141 may be configured to substantially vertically block the downstream opening 12b of the inlet pipe section 12 when no drainage is occurring, and a valve seat surface 12c configured to be able to abut against the valve element 141 when drainage backflows may be provided around the periphery of the downstream opening 12b of the inlet pipe section 12. This facilitates opening and closing of the valve element 141 when drainage is occurring, and prevents air from being forced upstream when drainage backflows, thereby preventing a seal failure in the drainage pipeline. In this case, if the valve seat surface is configured to diverge downstream from the inner circumferential surface to the end face of the inlet pipe section 12, the valve element 141 can reliably achieve a water-stopping effect even with a weaker force (water pressure) when drainage backflows.

[0057] <Example> In the following, examples will be described. In these examples, a scavenging test of the backflow prevention manhole 10 was conducted while changing the combination of the "height difference between the bottom of the downstream pipe and the bottom of the upstream pipe of the inflow pipe section 12" and the "height difference between the bottom of the drainage manhole body 11 and the bottom of the downstream pipe of the inflow pipe section 12" in the backflow prevention manhole 10.

[0058] Specifically, as shown in Fig. 4, in the backflow prevention manhole 10, four patterns of 0 mm, 10 mm, 20 mm, and 30 mm were set for the "difference in height between the downstream pipe bottom and the upstream pipe bottom of the inflow pipe section 12," and five patterns of 0 mm, 10 mm, 20 mm, 30 mm, and 40 mm were set for the "difference in height between the bottom of the drainage manhole main body 11 and the downstream pipe bottom of the inflow pipe section 12." Note that in Fig. 4, the same components as those of the backflow prevention manhole 10 shown in Fig. 2 are denoted by the same reference numerals. Also, due to the upstream piping (not shown) inserted into the first horizontal pipe section 121, the effective pipe bottom of the first horizontal pipe section 121 (the effective pipe bottom on the upstream side of the inflow pipe section 12) becomes higher by the wall thickness of the upstream piping, and the dimensions shown in Fig. 4 take this wall thickness into consideration.

[0059] In the drainage performance test, the drainage performance was evaluated by whether or not the wastewater (such as artificial waste) could pass through the backflow prevention basin 10 when it was flushed down the drainage pipe 1 shown in Figure 1 from a water-saving toilet, which is an indoor drainage system 2.

[0060] Drainage pipeline 1 consisted of an indoor pipe made of vinyl chloride pipe VU75 with a length of 1800 mm, and an outdoor pipe made of vinyl chloride pipe VU100 with a length of 11700 mm. Backflow prevention manhole 10 and other drainage manholes 3A, 3B, and 3C were placed in the outdoor piping portion of drainage pipeline 1. Specifically, drainage manhole 3A was placed 1300 mm downstream from the connection point between the indoor and outdoor piping, drainage manhole 3B was placed 4400 mm downstream from drainage manhole 3A, drainage manhole 3C was placed 1500 mm downstream from drainage manhole 3B, and backflow prevention manhole 10 was placed 4500 mm downstream from drainage manhole 3C. In addition, the flow gradient of the indoor piping is 1 / 100, there is a drop of 500 mm between the indoor piping and the outdoor piping, the flow gradient of the outdoor piping up to drainage manhole 3C is 2 / 100, and the flow gradient from drainage manhole 3C to backflow prevention manhole 10 is 1 / 200.

[0061] In addition, in the sweeping test, as a general rule, a large flush of the water-saving toilet is performed once, and if the flowing matter does not reach the backflow prevention manhole 10 and becomes stuck along the way, if the location where the flowing matter has stuck is upstream of the drainage manhole 3B, an additional large flush of the water-saving toilet is performed, and if the location where the flowing matter has stuck is at or downstream of the drainage manhole 3B, an additional small flush of the water-saving toilet is performed until the flowing matter reaches the backflow prevention manhole 10. The materials used for flushing were artificial dirt made from a PVA (polyvinyl alcohol) sponge (φ25, length 80mm, specific gravity approximately 1.05) (hereinafter referred to as PVA artificial dirt) and single toilet paper (one sheet is 90cm folded three times).The ``normal'' amount was four half-cut pieces of PVA artificial dirt and two single toilet paper sheets, and the ``large'' amount was six half-cut pieces of PVA artificial dirt, eight quarter-cut pieces of PVA artificial dirt and eight single toilet paper sheets.

[0062] The results of the scavenging test for various combinations of the "height difference between the bottom of the downstream pipe and the bottom of the upstream pipe of the inlet pipe section 12" in the backflow prevention manhole 10 and the "height difference between the bottom of the drainage manhole body 11 and the bottom of the downstream pipe of the inlet pipe section 12" are shown in Table 1 below, expressed as "(number of times the flowing material passed through the valve body 141 of the backflow prevention valve 14) / (number of tests)".

[0063] [Table 1]

[0064] As shown in Table 1, the scavenging ability of the backflow prevention manhole 10 is improved by positioning the downstream pipe bottom lower than the upstream pipe bottom in the inlet pipe section 12. Furthermore, when the "difference in elevation between the downstream pipe bottom and the upstream pipe bottom of the inlet pipe section 12" is the same, the scavenging ability of the backflow prevention manhole 10 is further improved by positioning the bottom of the drainage manhole body 11 lower than the downstream pipe bottom of the inlet pipe section 12. In particular, by making the "difference in elevation between the downstream pipe bottom and the upstream pipe bottom of the inlet pipe section 12" about 25 mm or more, more preferably 30 mm or more, sufficient scavenging ability can be obtained even for "large amounts" of flowing material. In this embodiment, the inner diameter of the pipe (vinyl chloride pipe VU100) connected to the inlet pipe section 12 from the upstream side is 107 mm, so it can be seen that particularly excellent sweeping properties can be obtained by making the "height difference between the downstream pipe bottom and the upstream pipe bottom of the inlet pipe section 12" approximately 23% or more of the inner diameter of the pipe connected to the inlet pipe section 12 from the upstream side.

[0065] As described above, if the flow gradient of the pipe connected to the inlet pipe section 12 from the upstream side (1 / 200 in this embodiment) is small, the flow rate of the wastewater in the pipe will be small and the flowing material will be more likely to stagnate, but the "height difference between the bottom of the pipe downstream and the bottom of the pipe upstream of the inlet pipe section 12" can improve the sweeping ability of the backflow prevention manhole 10.

[0066] Furthermore, if the "difference in elevation between the downstream pipe bottom and the upstream pipe bottom of the inlet pipe section 12" is set to approximately 50% or less of the outer diameter of the pipe connected to the inlet pipe section 12 from the upstream side, a general-purpose size fitting can be used for the inlet pipe section 12, which brings about cost benefits. Also, if the "difference in elevation between the downstream pipe bottom and the upstream pipe bottom of the inlet pipe section 12" is set to approximately 100% or less of the outer diameter of the pipe connected to the inlet pipe section 12 from the upstream side, it is possible to prevent the backflow prevention mass 10 from being buried deep in the ground, which brings about the benefit of improved workability.

[0067] In this example, in addition to the sweeping performance test described above, a retention test was conducted to evaluate whether a small amount of water flowing into the drainage pipeline 1 would accumulate upstream of the valve element 141 of the check valve 14 (whether the valve element 141 could be forced open). Specifically, 100 cc of water was flowed from the drainage manhole 3B, and an evaluation was made as to whether the entire 100 cc of water could pass through the downstream opening 12b of the inlet pipe section 12 without accumulating in front of the valve element 141. The retention test was conducted three times for each of two conditions: one in which the valve element 141 was naturally closed after normal drainage, and one in which the valve element 141 was manually pressed down to close the valve element 141, simulating a backflow of drainage water.

[0068] As a result of the retention test, with normal drainage, all 100 cc of water passed through the downstream opening 12b of the inlet pipe 12 regardless of whether the "difference in elevation between the downstream pipe bottom and the upstream pipe bottom of the inlet pipe 12" was 10 mm, 20 mm, or 30 mm. On the other hand, when simulating drainage after backflow, all 100 cc of water passed through the downstream opening 12b of the inlet pipe 12 if the "difference in elevation between the downstream pipe bottom and the upstream pipe bottom of the inlet pipe 12" was 20 mm or more.

[0069] Furthermore, it was confirmed that, in the case of a small amount of water, the valve element 141 does not open due to the drainage speed determined by the "difference in elevation between the downstream and upstream pipe bottoms of the inlet pipe section 12," but rather a small amount of water temporarily accumulates in front of the valve element 141, and the resulting hydraulic head pressure opens the valve element 141 to allow the water to pass through. From this, it was found that the "difference in elevation between the downstream and upstream pipe bottoms of the inlet pipe section 12" only needs to be an elevation difference that creates a water depth sufficient to apply sufficient hydraulic head pressure to the valve element 141. Furthermore, it was found that in order to prevent a small amount of water from accumulating, it is more effective to shorten the length of the horizontal pipe section (second horizontal pipe section 123) in front of the downstream opening 12b in the inlet pipe section 12 as much as possible, rather than the size of the "difference in elevation between the downstream and upstream pipe bottoms of the inlet pipe section 12."

[0070] (Other embodiments) In the above-described embodiment (including the examples, the same applies below), a backflow prevention sieve 10 is provided in a drainage pipeline 1 configured in series. However, this is not limited to this, and a backflow prevention sieve 10 may be provided in a drainage pipeline including multiple pipes configured in parallel using, for example, a drainage header or the like.

[0071] In addition, in the above embodiment, one inlet pipe section 12 and one outlet pipe section 13 for drainage are provided on the side wall of the drainage manhole body 11. However, this is not limited to this, and multiple inlet pipe sections 12 and multiple outlet pipe sections 13 may be provided on the side wall of the drainage manhole body 11.

[0072] In the above embodiment, the inflow pipe section 12 is composed of a first horizontal pipe section 121, an inclined pipe section 122, and a second horizontal pipe section 123. However, the configuration of the inflow pipe section 12 is not particularly limited as long as the downstream pipe bottom of the inflow pipe section 12 is located lower than the upstream pipe bottom, in other words, as long as the lower end of the downstream opening 12b of the inflow pipe section 12 is located lower than the lower end of the upstream opening 12a. For example, the first horizontal pipe section and / or the second horizontal pipe section 123 may not be provided. Alternatively, a third horizontal pipe section may be provided midway along the inclined pipe section 122.

[0073] In addition, in the above embodiment, the inlet pipe section 12 and the drainage manhole main body 11 are separate bodies, and the downstream side of the inlet pipe section 12 is inserted into the inside of the drainage manhole main body 11, but instead, the downstream end of the inlet pipe section 12 may be attached to the side wall of the drainage manhole main body 11, or the inlet pipe section 12 and the drainage manhole main body 11 may be molded integrally.

[0074] A longitudinal cross-sectional view of one modified example of the backflow prevention tank 10 is shown in Figure 5. Note that in Figure 5, the same components as those in the backflow prevention tank 10 shown in Figure 2 are assigned the same reference numerals. The modified example shown in Figure 5 differs from the backflow prevention tank 10 shown in Figure 2 in that the inlet pipe section 12 has a valve pipe 124 attached to the downstream side from the inside of the drainage tank body 11, and the downstream end face of the valve pipe 124 is provided with a valve seat surface 12c that can abut against the valve disc 141. According to this modified example, because the valve pipe 124, which is opened and closed by the valve disc 141, is attached from the inside of the drainage tank body 11, it is possible to attach the valve disc 141 integrally with the valve pipe 124, making it easier to assemble the backflow prevention tank.

[0075] In the modified example shown in FIG. 5, the second horizontal pipe section 123 may be positioned upstream compared to the backflow prevention basin 10 shown in FIG. 2, and the valve pipe 124 may be connected horizontally to the second horizontal pipe section 123 from the downstream side, and the valve pipe 124 may be configured as a part of the second horizontal pipe section 123. An extension section 111 extending inward of the drainage basin main body 11 may be provided on the inner wall around the opening 11b of the drainage basin main body 11, and the valve pipe 124 may be supported by the extension section 111. The valve pipe 124 may be inserted into the cylindrical extension section 111 and bonded to the extension section 111. The backflow prevention valve 14 (bearing member 15) may be attached to the top of the valve pipe 124. A recess 141a may be provided on the outer peripheral surface of the valve body 141, and a V-packing, for example, may be attached to the recess 141a as the packing 16. In this way, since the valve seat surface 12c is a tapered surface (inclined surface), the packing 16 adheres better to the valve seat surface 12c, and the water blocking effect of the valve body 141 when wastewater backflows is further increased.

[0076] Although the embodiments have been described above, it will be understood that various modifications in form and details are possible without departing from the spirit and scope of the claims. Furthermore, the above embodiments may be combined or substituted as appropriate as long as the functionality of the subject matter of the present disclosure is not impaired. Furthermore, the terms "first," "second," etc., described above, are used to distinguish the terms to which these terms are attached, and do not limit the number or order of the terms. [Explanation of symbols]

[0077] 1 Drainage line 2 Indoor drainage equipment 3A, 3B, 3C drainage mass 10 Backflow prevention tank 11 Drainage manhole body 11a, 11b opening 11c Protrusion 11d Inverter 111 Extension section 12 Inflow pipe section 12a Upstream opening 12b Downstream opening 12c Valve seat surface 121 1st horizontal pipe section 121a Steps 122 Inclined pipe section 123 2nd horizontal pipe section 123a Protrusion 124 Valve pipe 13 Outlet pipe section 13a Step 14 Check valve 141 Valve body 141a recess 142 Support part 143 Rotation axis 15 Bearing materials 16 Packing

Claims

1. A backflow prevention basin is installed in a drainage pipe connecting an indoor drainage system and a sewer pipe to prevent drainage water flowing backward through the drainage pipe from entering the upstream side. The drainage basin body, A drainage inlet pipe portion and a drainage outlet pipe portion provided on a side wall of the drainage basin body; a check valve provided in the drainage basin body and having a valve body configured to be able to close a downstream opening of the inlet pipe portion; Equipped with the valve element of the check valve closes the downstream opening of the inlet pipe section by its own weight when no drainage is performed, a downstream pipe bottom of the inlet pipe portion is located lower than an upstream pipe bottom of the inlet pipe portion; the inflow pipe section includes at least a first horizontal pipe section disposed upstream and having a horizontal or substantially horizontal pipe bottom, and an inclined pipe section disposed downstream of the first horizontal pipe section and having a pipe bottom inclined downward toward the downstream side; The inlet pipe section further includes a second horizontal pipe section that is arranged downstream of the inclined pipe section, is connected to the drainage basin body, and has a horizontal or approximately horizontal pipe bottom. Backflow prevention mass.

2. The bottom of the drainage basin body is located below the downstream pipe bottom of the inlet pipe section. The backflow prevention mass according to claim 1.

3. a height difference between the downstream pipe bottom and the upstream pipe bottom in the inlet pipe section is 23% or more of an inner diameter of a pipe connected to the inlet pipe section from the upstream side; The backflow prevention mass according to claim 1 or 2.

4. the first horizontal pipe section and the inclined pipe section are integrally formed, The inlet pipe portion is inserted into the drainage basin body, a valve seat surface that can come into contact with the valve body is provided on a downstream end surface of the inlet pipe portion; The backflow prevention mass according to any one of claims 1 to 3.

5. an extension line of the pipe axis of the first horizontal pipe section passes through the downstream opening of the inlet pipe section without intersecting with the inner wall surface of the inclined pipe section; The backflow prevention mass according to any one of claims 1 to 4.

6. The downstream side of the inlet pipe portion is inserted into the inside of the drainage basin body, The valve body vertically closes the downstream opening of the inlet pipe portion when no drainage is performed, a valve seat surface configured to be able to come into contact with the valve body when wastewater flows back, provided on a peripheral edge of the downstream opening of the inlet pipe section; The backflow prevention mass according to any one of claims 1 to 5.

7. The valve seat surface is provided in a shape that widens in the downstream direction from the inner circumferential surface to the end surface of the inlet pipe portion. The backflow prevention mass according to claim 6.

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