Flow path forming member and flow path forming structure

Abstract

To provide a flow path forming member that enables the water level to rise above a normal storage level without the need for manual operation even during heavy rainfall.SOLUTION: A flow path forming member is disposed between a water level adjustment mechanism 110 and a drainage channel 108 communicating the inside and the outside of an outlet chamber 100, in an outlet chamber 100 of a paddy field in which the water level adjustment mechanism 110 is provided to restrict inflow of water into the outlet chamber 100. The member has a tubular shape, and includes an inlet 12 which can be positioned above the water level adjustment mechanism 110 and allows water to flow in, and an outlet 16 which allows water to flow out to the drainage channel 108, and has an overflow flow path connecting the inlet 12 and the outlet 16 which are formed inside. In addition, a junction port 19 is provided to join water that has flowed into the outlet chamber 100 over the water level adjustment mechanism 110 with the overflow flow path between the inlet 12 and the outlet 16. The flow path cross-sectional areas of the inlet 12 and the overflow flow path are larger than the flow path cross-sectional area of the junction port 19.SELECTED DRAWING: Figure 15

Description

[Technical Field]

[0001] The present invention relates to a channel-forming member to be installed in a rice paddy outlet basin, and a channel-forming structure including the channel-forming member. [Background technology]

[0002] Conventionally, water channels in rice paddies are equipped with outlet manholes, and when storing water in the paddy fields, a water level adjustment mechanism such as a wooden board is attached to the outlet manhole to prevent water from flowing out, and when draining water from the paddy field, the water level adjustment mechanism attached to the outlet manhole is removed.

[0003] Another water level adjustment device that can easily adjust the water level in rice paddies is described in Patent Document 1. The water level adjustment device described in Patent Document 1 has an elbow pipe attached to a standard weir plate fitted into a water outlet basin installed in the rice paddy, and the water level in the rice paddy can be adjusted by changing the height of the elbow pipe. When using this water level adjustment device, in the event of heavy rain, by attaching a cover to the elbow pipe, water can be stored up to a water level higher than the upper end of the elbow pipe, thereby preventing a sudden increase in the amount of water discharged into the river. In addition, an overflow hole is provided near the upper end of the standard weir plate, and if the water level rises too much while the cover is attached to the elbow pipe, water is discharged from the overflow hole, thereby preventing water from overflowing from the banks of the rice paddy. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2023-121320 Summary of the Invention [Problem to be solved by the invention]

[0005] The water level adjustment device described in Patent Document 1 requires the installation of a cover on the elbow pipe during heavy rain, and if this work is not performed, the water storage effect during heavy rain cannot be achieved.

[0006] The present invention has been made to solve the above-mentioned problems, and its main object is to provide a flow path forming member that can maintain a water level higher than the normal water storage capacity without requiring any work, even during heavy rain. [Means for solving the problem]

[0007] The first configuration is a flow path forming member that is placed within a rice paddy outfall manhole, which is equipped with a water level adjustment mechanism that limits the flow of water into the manhole, between the water level adjustment mechanism and a drainage channel that connects the inside and outside of the manhole, the member being cylindrical and capable of being placed above the water level adjustment mechanism and having an inlet through which water can flow, and an outlet through which water can flow into the drainage channel, an overflow flow path connecting the inlet and outlet is formed inside, and a confluence port is provided that allows water that has flowed into the manhole over the water level adjustment mechanism to merge between the inlet and outlet of the overflow flow path, and the flow path cross-sectional area of ​​the inlet and the overflow flow path is larger than the flow path cross-sectional area of ​​the confluence port.

[0008] In the first configuration, the inlet of the overflow channel can be positioned above the water level adjustment mechanism, so water can accumulate up to the inlet of the overthrow channel during heavy rain without changing the height of the water level adjustment mechanism. Furthermore, if the water level rises above the water level adjustment mechanism, it is possible to drain water through the confluence before the water level reaches the inlet. Therefore, draining water through the confluence can slow the rise in water level, and once the water level reaches the inlet, draining water through the overflow channel, which has a larger cross-sectional area than the confluence, can prevent the water level from rising further.

[0009] The second configuration includes, in addition to the first configuration, a connecting tube that can be fitted into the drainage channel, and the outflow port is provided in the connecting tube.

[0010] In the second configuration, water can be discharged from the outlet into the drainage channel, thereby improving the efficiency of drainage.

[0011] In the third configuration, in addition to the second configuration, the cross-sectional area of ​​the flow path of the junction port is smaller than the cross-sectional area of ​​the flow path of the outflow port.

[0012] In the third configuration, the discharge of water through the confluence port can be restricted, so that when the water level exceeds the height of the water level adjustment mechanism and is lower than the height of the inlet, water can be stored while preventing excessive discharge of water.

[0013] In the fourth configuration, in addition to the third configuration, an annular anti-slip member that suppresses relative rotation between the connecting tube and the drainage channel is fitted onto the outer periphery of the connecting tube.

[0014] When the flow path forming member is attached to the drainage channel with adhesive, screws, or other fixing means, the relative position of the flow path forming member to the drainage channel can be easily maintained, but removing it for maintenance requires complicated work. In this regard, the fourth configuration attaches the connecting tube by fitting it into the drainage channel, and then the relative rotation is suppressed by the anti-slip member, so it is possible to maintain the position while also making maintenance easy.

[0015] The fifth configuration is the same as any one of the first to fourth configurations, except that a thin portion is formed in the peripheral wall that constitutes the outer periphery of the overflow channel.

[0016] In the fifth configuration, since it is possible to easily cut along the thin portion, the height of the flow path forming member can be changed according to the height of the ridges in the rice paddy field, etc.

[0017] The sixth configuration is a flow path forming structure in a water outlet manhole having a pair of opposing side walls of the manhole and a drainage channel connecting the inside and outside, and comprising a water level adjustment mechanism provided between the side walls to restrict the flow of water into the manhole, and a flow path forming member of the first configuration, wherein the flow path forming member is attached to the manhole so that the position of the inlet is higher than the water level adjustment mechanism and lower than the paddy field ridge on which the manhole is installed, and the flow path cross-sectional area of ​​the inlet and the overflow flow path is larger than the flow path cross-sectional area of ​​the confluence, which is smaller than the flow path cross-sectional area of ​​the drainage channel.

[0018] In a sixth configuration, a flow path forming structure can be provided that includes the flow path forming member of the first configuration.

[0019] In the seventh configuration, in addition to the sixth configuration, the flow path forming member is provided with the outflow outlet and a connecting tube that can be fitted into the drainage channel, and an anti-slip member that suppresses relative rotation is provided between the outer surface of the connecting tube and the inner surface of the drainage channel, so that when the flow path forming member rotates around the central axis of the connecting tube, the flow path forming member abuts against the drop manhole and the inflow opening is maintained at a position higher than the upper end of the water level adjustment mechanism.

[0020] When the flow path forming member is attached to the drainage channel with adhesive, screws, or other fastening means, the relative position of the flow path forming member to the drainage channel can be easily maintained, but removing it for maintenance requires cumbersome work. In this regard, the seventh configuration attaches the connecting tube to the drainage channel by fitting it inside, and then uses an anti-slip member to prevent relative rotation, thereby achieving both the effect of maintaining the position and ease of maintenance. Furthermore, although an anti-slip member is provided, the flow path forming member is more likely to rotate than when using fastening means such as adhesive or screws. Even when the flow path forming member rotates, the flow path forming member abuts against the drainage channel, maintaining the inlet at a position higher than the upper end of the water level adjustment mechanism. This ensures a water-stopping effect even when the water level exceeds the upper end of the water level adjustment mechanism. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 10 is a perspective view showing a state in which a flow path forming member is attached to a drop manhole. [Figure 2] This is an oblique view of a drop-off manhole. [Figure 3] This is a front view of the drop-off manhole. [Figure 4] This is a plan view of the drop-off manhole. [Figure 5] FIG. [Figure 6] FIG. [Figure 7] FIG. [Figure 8] FIG. [Figure 9] FIG. [Figure 10] Cross-sectional view taken along line AA. [Figure 11] FIG. 11 is an enlarged view of FIG. [Figure 12] FIG. 10 is a front view showing a state in which a flow path forming member is attached to the inlet manhole. [Figure 13] FIG. 10 is a plan view showing a state in which a flow path forming member is attached to a drop manhole. [Figure 14] FIG. 10 is a front view with the water level adjustment mechanism removed. [Figure 15] Cross-sectional view taken along line BB. [Figure 16] 10 is a diagram showing the state in which the water level in the rice paddy exceeds the upper end of the water level adjustment mechanism. [Figure 17] FIG. 10 is a diagram showing the state in which the water level in the rice paddy exceeds the upper end of the flow path forming member. [Figure 18] FIG. 10 is a diagram showing a state in which the flow path forming member is tilted. [Figure 19] 10A and 10B are diagrams illustrating a state in which the height of the flow path forming member is changed. DETAILED DESCRIPTION OF THE INVENTION

[0022] As shown in Fig. 1, the flow path forming member 10 according to the embodiment is attached to an outlet manhole 100 provided in a water conduit in a paddy field. In the following description, the top-bottom direction is the up-down direction, the paddy field side of the water conduit is the forward direction, and the width direction of the water conduit is the left-right direction.

[0023] First, the structure of the inlet manhole 100 will be described with reference to Figures 2-4. The inlet manhole 100 is integrally cast from concrete. The inlet manhole 100 includes a bottom plate 101, which is a generally square, flat plate extending in the front-to-rear direction. A bottom groove 102 extending in the left-to-right direction parallel to the front and rear ends is formed slightly toward the front end of the bottom plate 101 in the front-to-rear direction. Flat side walls 103, 104, which extend upward and have a generally uniform thickness in the left-to-right direction, are provided opposite the left and right ends of the bottom plate 101. The side walls 103, 104 have the same shape, with the front end lower than the rear end, and their height gradually decreasing from the rear end to the front end. Side wall grooves 105, 106, which extend upward, are provided on the inner surfaces of the side walls 103, 104 at the same front-to-rear position as the bottom groove 102.

[0024] A flat rear wall 107 that stands upward and has a uniform thickness in the front-to-rear direction is provided at the rear ends of the bottom plate 101 and the side walls 103, 104. A cylindrical drainage channel 108 that penetrates in the front-to-rear direction is provided near the lower end of this rear wall 107. The center of this drainage channel 108 is approximately aligned with the center of the rear wall in the left-to-right direction, and the diameter of the drainage channel 108 is approximately half the width of the rear wall 107.

[0025] A water level adjustment mechanism 110 is attached to the water outlet manhole 100 configured as described above. This water level adjustment mechanism 110 is a rectangular plate made of wood, plastic, metal, etc., and multiple mechanisms of different heights are available depending on the required water level. This water level adjustment mechanism 110 is installed by being inserted into the side wall grooves 105, 106 from above.

[0026] Next, the flow path forming member 10 according to this embodiment will be described with reference to FIGS. 5-11. The flow path forming member 10 includes a rectangular tubular portion 11 that extends in the vertical direction and has a rounded rectangular cross section. The rectangular tubular portion 11 has a width greater in the left-right direction than in the front-to-rear direction, and the width in the left-to-right direction is smaller than the distance between the side walls 103, 104 of the outlet manhole 100. The height in the vertical direction is greater than the width in the left-to-right direction. The rectangular tubular portion 11 has an open upper end, which is referred to as the inlet 12. The inner surface of the rectangular tubular portion 11 is flat from the upper end to the lower end. Meanwhile, a groove 13 recessed toward the inner surface is formed on the outer surface of the rectangular tubular portion 11 so as to extend horizontally around the periphery of the rectangular tubular portion 11 in the front-to-rear and left-to-right directions. A plurality of grooves 13 (seven in this embodiment) are provided at intervals in the vertical direction. Since the groove 13 is provided in this manner and the inner surface of the rectangular tube portion 11 is flat, the portion where the groove 13 is provided is thin-walled, and the portion where the groove 13 is provided can be called the thin-walled portion.

[0027] The lower end of the rectangular tubular portion 11 is provided with a semicircular lower end portion 14 that bulges downward when viewed from the front. The rectangular tubular portion 11 and the lower end portion 14 form an inner surface that is continuous in the vertical direction on the front and left and right side surfaces. Meanwhile, a cylindrical connecting tube 15 that protrudes rearward is provided on the rear side near the lower end of the rectangular tubular portion 11 and on the rear side of the lower end portion 14. The rear end of this connecting tube 15 is open, and this open rear end is referred to as the outflow port 16. The outer diameter of this connecting tube 15 is slightly smaller than the inner diameter of the drainage channel 108 of the inlet manhole 100.

[0028] A recessed groove 17 is formed around the outer periphery of the connecting tube 15, and an annular packing 18 made of elastic resin is attached to the groove 17. The inner diameter of the packing 18 is approximately equal to the outer diameter of the portion of the connecting tube 15 where the groove 17 is provided, and the outer diameter of the packing 18 is slightly larger than the inner diameter of the drainage channel 108.

[0029] A junction port 19, which is a hole that penetrates in the front-rear direction, is provided on the front side of the lower end portion 14. The diameter of this junction port 19 is approximately equal to the front-rear width of the inner surface of the square tubular portion 11. In other words, the area of ​​the junction port 19 is smaller than the cross-sectional area of ​​the square tubular portion 11 and the cross-sectional area of ​​the connecting tube 15. Therefore, the cross-sectional area of ​​the junction port 19 is smaller than the cross-sectional areas of the inlet 12, the square tubular portion 11, the lower end portion 14, the connecting tube 15, and the outlet 16.

[0030] When the flow path forming member 10 described above is attached to the inlet 100 and used as a flow path forming structure, the connecting tube 15 is inserted into the drainage channel 108 and fitted therein, as shown in FIGS. 1 and 12-15 . At this time, the upper end of the flow path forming member 10 (the position of the inlet 12) is positioned below the upper end of the rear wall 108. When the connecting tube 15 is attached to the drainage channel 108, the gasket 18 attached to the connecting tube 15 elastically deforms and collapses, filling the small gap between the outer surface of the connecting tube 15 and the inner surface of the drainage channel 108, thereby preventing water from leaking through the gap. Because the gasket 18 is elastically deformed, the coefficients of friction between the outer surface of the gasket 18 and the inner surface of the drainage channel 108 and between the inner surface of the gasket 18 and the groove 17 of the connecting tube 15 increase, thereby preventing the connecting tube 15 from rotating around its central axis. Therefore, the gasket 18 can be referred to as an anti-slip member. In this embodiment, the flow path forming member 10 is attached to the inlet manhole 100 simply by inserting the connecting tube 15 into the drainage channel 108 and fitting it inside, but various well-known fixing means may also be added to attach the flow path forming member 10 to the inlet manhole 100.

[0031] Next, a case where the water level in the paddy field rises when the outlet manhole 100 to which the flow path forming member 10 and the water level adjustment mechanism 110 are attached is described with reference to Figures 16 and 17. Note that when the water level in the paddy field does not reach the upper end of the water level adjustment mechanism 110, the water is blocked by the water level adjustment mechanism 110, and therefore illustrations and detailed explanations are omitted.

[0032] First, a case where the water level in the rice paddy rises due to rainfall and becomes higher than the upper end of the water level adjustment mechanism 110 will be described with reference to Figure 16. In Figure 16, the two-dot chain line indicates the water level in the rice paddy. In this case, water that exceeds the upper end of the water level adjustment mechanism 110 seeps into the gap between the water level adjustment mechanism 110 and the flow path forming member 10 in the outlet manhole 100. The water that seeps into the gap between the water level adjustment mechanism 110 and the flow path forming member 10 in the outlet manhole 100 flows into the confluence port 19 of the flow path forming member 10, passes through the lower end 14 of the flow path forming member 10 and the inside of the connecting tube 15, flows out of the outlet 16 into the drainage channel 108, and is then discharged from the drainage channel 108 to the outside of the outlet manhole 100.

[0033] Next, a case where the water level in the rice paddy further rises due to heavy rain and exceeds the upper end of the channel-forming member 10 will be described with reference to FIG. 17 . This situation can occur when the water level in the rice paddy exceeds the upper end of the water-level adjustment mechanism 110, and water is released through the channel leading from the confluence port 19 to the drainage channel 108, but the amount of water increase due to rainfall exceeds the amount of water released. In FIG. 17 , the two-dot chain line again indicates the water level in the rice paddy. In this case, water that has exceeded the upper end of the channel-forming member 10 flows into the channel-forming member 10 through the inlet 12 of the channel-forming member 10. The water that has flowed into the channel-forming member 10 passes through the rectangular tube portion 11, the lower end 14, and the inside of the connecting tube 15. Water also flows in through the confluence port 19, flows out of the outlet 16 into the drainage channel 108, and is then released from the drainage channel 108 to the outside of the outlet manhole 100.

[0034] The flow path through which water flowing in from inlet 12 passes through square tubular portion 11, lower end 14, and connecting tube 15 to outlet 16 is used when the water level rises above the upper end of water level adjustment mechanism 110, and can be said to be a flow path for suppressing water flooding (overflow), so this flow path is called the overflow flow path. Furthermore, the flow path cross-sectional area of ​​confluence port 19 can be said to be smaller than the flow path cross-sectional area of ​​inlet 12, the flow path cross-sectional area of ​​the overflow flow path, and the flow path cross-sectional area of ​​outlet 16, and it can be said that confluence port 19 causes water that has flowed into drop-out manhole 100 to merge with the overflow flow path.

[0035] The flow path forming member 10 used as described above is attached by inserting the connecting tube 15 into the drainage channel 108, and although rotation is suppressed by the gasket 18, which is an anti-slip member, the member is not fixed in place. Therefore, water pressure or the like may cause the flow path forming member 10 to rotate about the central axis of the connecting tube 15. In this case, as shown in FIG. 18 , the upper end of the rectangular tube portion 11 of the flow path forming member 10 abuts against the side walls 103, 104 of the outlet manhole 100, suppressing further rotation. Therefore, even if the flow path forming member 10 rotates about the central axis of the connecting tube 15, the position of the upper end of the flow path forming member 10 is maintained at a position higher than the upper end of the water level adjustment mechanism 110.

[0036] When using the above-described channel-forming member 10, depending on various conditions such as the height of the ridges and the depth of the inlet sump 100, it may be necessary to lower the height of the channel-forming member 10, as shown in FIG. 19 . That is, when the water level in a rice paddy rises due to heavy rain and reaches the upper end of the channel-forming member 10 according to this embodiment, if the water level is higher than the ridges, the ridges will be submerged. In such a case, the height can be changed by cutting along the grooves 13 of the channel-forming member 10 with a blade or the like. Note that FIG. 19 shows an example in which cutting is performed along the second groove 13 from the top. Note that when changing the height of the channel-forming member 10, it is necessary to set the channel-forming member 10 at a height such that, when the channel-forming member 10 is attached to the inlet sump 100, the upper end of the channel-forming member 10 is positioned higher than the upper end of the water level adjustment 110. Furthermore, even when the flow path forming member 10 rotates around the central axis of the connecting tube 15, it is preferable to change the height of the flow path forming member 10 so that the upper end of the flow path forming member 10 abuts against the side walls 103, 104 and is higher than the upper end of the water level adjustment mechanism 110.

[0037] With the above-described configuration, the flow path forming member 10 according to this embodiment and the flow path forming structure using the flow path forming member 10 have the following advantages.

[0038] Since the inlet 12 of the overflow channel can be positioned above the water level adjustment mechanism 110, water can be accumulated up to the position of the inlet 12 of the overflow channel during heavy rain without changing the height of the water level adjustment mechanism 110.

[0039] When the water level becomes higher than the water level adjustment mechanism 110, it is possible to drain water through the confluence port 19 before the water level reaches the position of the inlet 12. Therefore, draining water through the confluence port 19 can slow down the rise in water level, and when the water level reaches the position of the inlet 12, draining water through the overflow channel, which has a larger cross-sectional area than the confluence port 19, can prevent the water level from rising further.

[0040] The connecting tube 15 is attached by inserting it into the drainage channel 108 and fitting it inside, so that water can be drained from the outlet 16 into the drainage channel 108, thereby improving the efficiency of drainage.

[0041] Since the confluence port 19 is smaller than the inlet port 12, the amount of water discharged through the confluence port 19 can be limited, and when the water level exceeds the height of the water level adjustment mechanism 110 and is lower than the height of the inlet port 12, water can be stored while preventing excessive water discharge.

[0042] When the flow path forming member 10 is attached to the outlet manhole 100 with a fixing means such as adhesive or screws, the relative position of the flow path forming member 10 to the outlet manhole 100 can be easily maintained, but removing it for maintenance requires complicated work. In this regard, in this embodiment, the connecting tube 15 is attached by fitting it into the drainage channel 108, and relative rotation is suppressed by the anti-slip member 18, so it is possible to achieve both the effect of maintaining the position and ease of maintenance.

[0043] Since the flow path forming member 10 can be easily cut along the thin portion where the grooves 13 are formed, the height of the flow path forming member 10 can be changed according to the height of the paddy field ridges, etc.

[0044] Although the gasket 18 prevents the flow path forming member 10 from rotating, it can be said that the flow path forming member 10 is more likely to rotate than when fixing means such as adhesives or screws are used. In this regard, in this embodiment, even when the flow path forming member 10 rotates, the flow path forming member 10 abuts against the side walls 103, 104 of the outlet manhole 100, and the inlet 12 is maintained at a position higher than the upper end of the water level adjustment mechanism 110. Therefore, even when the flow path forming member 10 rotates and the water level becomes higher than the upper end of the water level adjustment mechanism 110, a water-stopping effect can be obtained.

[0045] Since the left-right width of the rectangular tubular portion 11 of the flow path forming member 10 is smaller than the distance between the side walls 103, 104 of the inlet manhole 100, it can be attached to inlet manholes 100 even if the side walls 103 have different left-right widths.

[0046] <Modification> In the embodiment, the flow path forming member 10 includes a rectangular tubular portion 11 having a cross section with rounded corners, but the shape of the flow path forming member 10 is not limited to this. Various shapes can be adopted, such as a cylindrical shape or a shape in which the front-to-back width is greater than the left-to-right width. Even in these cases, it is sufficient that the flow path cross-sectional area of ​​the structure corresponding to the inlet 12 and the structure corresponding to the overflow flow path is greater than the flow path cross-sectional area of ​​the structure corresponding to the junction port 19. Furthermore, the shape of the connecting tube 15 in which the outlet 16 is provided can be changed as appropriate depending on the shape of the drainage channel 108 of the inlet pit 100.

[0047] In the embodiment, a gasket 18, which is an anti-slip member, is provided on the outer periphery of the connecting tube 15, but it is also possible to maintain the relative position by friction between the outer periphery of the connecting tube 15 and the inner periphery of the drainage channel 108 without providing the gasket 18.

[0048] In the embodiment, the flow path forming member 10 is attached to the outlet manhole 100 by fitting the connecting tube 15 into the drainage channel 108. However, the connecting tube 15 may not be provided, and a structure corresponding to the lower end portion 14 may be located close to the drainage channel 108. In this case, the rear end of the lower end portion 14 corresponds to the outlet 16, and water is released from the structure corresponding to the drainage channel 108 into the nearby drainage channel 108. In this case, the flow path forming member 10 may be attached to the outlet manhole 100 by known attachment means such as adhesive or screws. Alternatively, the left-right width of the flow path forming member 10 may be made approximately equal to the distance between the side walls 103, 104 of the outlet manhole 100, and the flow path forming member 10 may be attached by friction between both side surfaces of the flow path forming member 10 and the side walls 103, 104.

[0049] In the embodiment, the water level adjustment mechanism 110 is a single plate, but it may be configured with multiple plates whose height can be changed. Also, the water level adjustment device described in JP 2023-121320 A, which has been presented as a prior art document, may be used instead of the water level adjustment mechanism 110 according to the present embodiment.

[0050] In the embodiment, the flow path forming member 10 is formed by integral molding, but it may also be formed by combining multiple tubular members. In this case, if it is possible to combine multiple members in the vertical direction for the configuration corresponding to the rectangular tubular portion 11, the height of the flow path forming member 10 can be changed by changing the number of multiple members to be combined.

[0051] In the embodiment, the inlet 12 is open upward, but it may be open toward the front side of the water channel forming member 10.

[0052] In the embodiment, only one inlet 12 is provided at the top end of the rectangular tubular portion 11, but multiple inlets may be provided on the front or side of the rectangular tubular portion 11. This allows the amount of water discharged to increase as the water level rises. In this case, the total cross-sectional area of ​​the flow paths of the multiple inlets should be larger than the cross-sectional area of ​​the flow path of the junction port 19. In addition, when an inlet is provided on the front or side of the rectangular tubular portion 11, it may be provided by drilling a hole in the recessed groove 13.

[0053] In the embodiment, the number of confluence ports 19 is one, but multiple ports may be provided. In this case, if multiple confluence ports are arranged vertically, the amount of discharged water can be increased as the water level between the water level adjustment mechanism 110 and the water channel forming member 10 rises before the water level reaches the upper end of the inlet 12. In this case, the total flow path cross-sectional area of ​​the multiple confluence ports only needs to be smaller than the flow path cross-sectional area of ​​the inlet 12, the flow path cross-sectional area of ​​the overflow flow path, and the flow path cross-sectional area of ​​the outlet 16. [Explanation of symbols]

[0054] Flow path forming member...10, square tube portion...11, inlet...12, groove...13, lower end...14, connecting tube...15, outlet...16, packing...18, confluence...19, drop box...100, drainage channel...108, water level adjustment mechanism...110

Claims

1. A flow path forming member is disposed in a paddy field outlet manhole, in which a water level adjustment mechanism is provided to limit the inflow of water into the outlet manhole, between the water level adjustment mechanism and a drainage channel that communicates the inside and outside of the outlet manhole, a cylindrical inlet that can be positioned above the water level adjustment mechanism and through which water can flow, and an outlet that can discharge water to the drainage channel, and an overflow flow path that connects the inlet and the outlet is formed inside; a confluence port is provided between the inlet and the outlet of the overflow channel to allow the water that has flowed into the outlet basin beyond the water level adjustment mechanism to join the water, A flow path forming member, wherein the flow path cross-sectional areas of the inlet and the overflow flow path are larger than the flow path cross-sectional area of ​​the junction port.

2. The flow path forming member according to claim 1 , wherein the water channel forming tube includes a connecting tube that can be fitted into the drainage channel, and the outlet is provided in the connecting tube.

3. The flow path forming member according to claim 2 , wherein a flow path cross-sectional area of ​​the junction port is smaller than a flow path cross-sectional area of ​​the outflow port.

4. The flow path forming member according to claim 2 , wherein an annular anti-slip member is fitted onto the outer periphery of the connecting tube to suppress relative rotation between the connecting tube and the drainage channel.

5. 5. The flow path forming member according to claim 1, wherein a thin portion having a small thickness is formed on a peripheral wall that constitutes an outer periphery of the overflow flow path.

6. A flow path forming structure in a water outlet comprising a pair of opposing side walls of the water outlet and a drainage channel communicating the inside and outside of the water outlet, a water level adjustment mechanism provided between the side walls and configured to limit the inflow of water into the outlet basin; The flow path forming member according to claim 1, the flow path forming member is attached to the water inlet so that the position of the inlet is higher than the water level adjustment mechanism and lower than the ridge of the paddy field on which the water inlet is installed, A flow path forming structure in a drop-out basin, wherein the flow path cross-sectional area of ​​the confluence is smaller than the flow path cross-sectional area of ​​the drainage channel.

7. the flow path forming member is provided with the outflow port and includes a connecting tube that can be fitted into the drainage channel, An anti-slip member is provided between the outer surface of the connecting tube and the inner surface of the drainage channel to suppress relative rotation, A flow path forming structure as described in claim 6, wherein when the flow path forming member rotates around the central axis of the connecting tube, the flow path forming member abuts against the drop manhole and the inlet is maintained at a position higher than the upper end of the water level adjustment mechanism.

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