Backflow prevention joint and backflow prevention system equipped with the same

Abstract

To provide backflow prevention means having a rotary part such as a hinge for rotating a valve body, in which the valve body is prevented from becoming inoperative due to foreign matter contained in drainage.MEANS FOR SOLVING THE PROBLEM: A backflow prevention joint comprises a valve body, a valve tube having an inlet opening and an outlet opening forming a valve seat part in contact with the valve body, a hinge part provided at a marginal part of the valve body, and a hinge support part disposed at a side of the hinge part to rotatably support the hinge part and provided at an upper part of the valve tube. A protective cover is provided at upper parts of the hinge part and the hinge support part to cover all or a part of the hinge part and the hinge support part. A backflow prevention system comprising the joint is also provided.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a backflow prevention joint and a backflow prevention system equipped with the joint, and in particular to a backflow prevention joint equipped with an anti-adhesion cover that covers the hinge portion of a valve body rotatably supported on a valve pipe, and a backflow prevention system having a T-shaped cylindrical body equipped with the joint. [Background technology]

[0002] Generally, wastewater discharged from drainage facilities such as toilets in houses is collected in drainage manholes installed within residential areas via drainage pipes connected to each drainage facility in order to mitigate sudden changes in the amount of wastewater or to allow for the removal and inspection of foreign objects such as garbage. The wastewater collected in the drainage manholes then flows out into the main sewer pipe via a public manhole or manhole.

[0003] However, when a large amount of rainwater flows into the main sewer pipe in a short period of time, the drainage capacity of the main sewer pipe is exceeded, and the overflowing wastewater flows back through catch basins, etc., causing the problem of the backflowing wastewater spewing out from indoor drainage equipment connected to the drain pipe.

[0004] Therefore, in order to prevent wastewater backflowing from the sewer main pipe from overflowing from indoor drainage equipment through a drainage manhole, etc., a joint pipe with a check valve attached to the inlet of the drainage manhole, as described in, for example, JP 2020-176507 A (Patent Document 1), and a drainage manhole with a backflow prevention valve as described above attached to the inlet, as described in, for example, FIG. 2 of JP 2021-169701 A (Patent Document 2), have been developed. In this way, in recent years, measures have been taken to prevent backflow when a large amount of rainwater is generated in a short period of time due to abnormal weather, etc. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2020-176507 A [Patent Document 2] Patent Publication No. 2021-169701 Summary of the Invention [Problem to be solved by the invention]

[0006] However, when wastewater containing foreign matter such as filth flows into the backflow prevention means from the drainage equipment inside the house, and when the amount of wastewater is particularly large, the wastewater may become violent near the backflow prevention means and may bounce back into the backflow prevention means after colliding with the wall. Therefore, with the backflow prevention means as described above, there is a problem that filth and the like adheres or accumulates on the hinge portion for rotating the valve body, and eventually the valve body becomes inoperable due to the adhered matter solidifying.

[0007] Therefore, the present invention aims to provide a backflow prevention means having a rotating part such as a hinge for rotating the valve body, in which the valve body is prevented from becoming inoperable due to foreign matter contained in the wastewater. [Means for solving the problem]

[0008] After extensive research into the structure of the backflow prevention means and the flow of wastewater, the inventors discovered that in terms of the structure of the backflow prevention means, it is extremely effective to provide anti-adhesion covers on rotating parts such as hinges, and in terms of the flow of wastewater passing through the backflow prevention means, it is extremely effective to align the inlet and outlet at right angles in order to reduce wastewater that rebounds into the backflow prevention means, and thus completed the present invention.

[0009] That is, according to the present invention, in a backflow prevention joint comprising a valve body, a valve pipe having an inlet opening and an outlet opening forming a valve seat portion that abuts the valve body, a hinge portion provided on the peripheral portion of the valve body, and a hinge support portion provided on the upper portion of the valve pipe and arranged on the side of the hinge portion to rotatably support the hinge portion, a backflow prevention joint is provided which has an anti-adhesion cover arranged on the upper portion of the hinge portion and the hinge support portion so as to cover all or part of the hinge portion and the hinge support portion.

[0010] According to the present invention, the backflow prevention fitting is provided with an anti-adhesion cover that covers the upper part of the rotating part such as a hinge for rotating the valve body, thereby preventing foreign matter such as filth contained in the wastewater from adhering to or accumulating on the rotating part such as the hinge, and preventing the movement of the valve body from being hindered by adhering matter.

[0011] Furthermore, the backflow prevention joint of the present invention may be attached as a backflow prevention system to the inlet of a T-shaped cylindrical body having an inlet that opens horizontally, an outlet that communicates with the inlet and opens downward, and an inspection hatch that communicates with the inlet and the outlet and opens upward. Note that in this specification, "downward" and "upward" are sufficient as long as they are "downward" or "upward" facing in a substantially vertical direction, and do not mean "vertically downward" or "vertically upward" facing in a vertical direction in the strict sense.

[0012] In addition, in the backflow prevention system of the present invention, in order to increase the freedom of the piping diameter that can be connected to the outlet, a different diameter socket having an outer peripheral portion with an outer diameter the same as the inner diameter of the outlet and an inner peripheral portion with an inner diameter smaller than the outer diameter of the outer peripheral portion can be attached to the outlet.

[0013] According to the backflow prevention system of the present invention, the outflow outlet is positioned perpendicular to the inflow inlet so that wastewater that passes through the backflow prevention joint in a substantially horizontal direction falls freely under its own weight when it flows out of the outlet opening of the backflow prevention joint. This makes it possible to significantly reduce the amount of wastewater that bounces back into the backflow prevention joint directly or by colliding with a wall surface, etc., even when the amount of wastewater is large, and significantly reduces the risk of foreign matter contained in the wastewater adhering to the hinge portion, etc.

[0014] In the backflow prevention joint of the present invention, the adhesion prevention cover can be detachably attached to the hinge support part in order to improve the maintainability. When the adhesion prevention cover is detachably attached using the hinge support part of the valve pipe, it is preferable to provide the adhesion prevention cover with a clamp part that can clamp the outer periphery of the hinge support part, for example.

[0015] In the backflow prevention joint of the present invention, the adhesion prevention cover may be disposed so as to restrict the rotation range of the valve body (hinge portion) by abutting against the hinge portion. The rotation range of the valve body can be restricted by disposing the downstream end of the adhesion prevention cover away from the hinge portion in the valve body that is suspended by its own weight when there is no drainage or the drainage amount is small and the drainage pressure acting on the valve body by colliding with it is unloaded, for example.

[0016] In a backflow prevention joint, if the rotation range of the valve body to the opening side becomes too large, backflow water may collide with the upstream back surface of the valve body when a backflow occurs, and the valve body may not be able to operate to the closing side. Therefore, in the present invention, the adhesion prevention cover functions as a stopper that restricts the rotation range of the valve body, so that backflow water is sure to collide with the downstream surface of the valve body, and the valve body can be sure to rotate to the closing side without malfunctioning due to backflow water.

[0017] In the backflow prevention joint of the present invention, it is preferable that the downstream surface of the valve body is flat and the upstream back surface is bulged toward the upstream side. In this case, it is preferable to form a space between the downstream surface and the upstream back surface of the valve body.

[0018] In the present invention, when the valve body is shaped as described above, the upstream back surface of the valve body, which bulges from the downstream side to the upstream side, does not receive a large force even when wastewater collides with it, but the downstream surface of the flat valve body receives a large force when wastewater collides with it.Therefore, when backflow occurs, the backflow water mainly collides with the downstream surface of the valve body, making it possible to rotate the valve body to the closing side more reliably.

[0019] In addition, by providing a space between the downstream surface and the upstream back surface of the valve disc, buoyancy is generated in the space when the valve disc is immersed in backflow water, and the valve disc can stably maintain the closed state in which it abuts against the valve seat, thereby reliably preventing the backflow of wastewater. Although not shown, the buoyancy generating portion can be constructed by attaching a member with a specific gravity smaller than that of water, such as polystyrene foam, to the upstream back surface of the valve disc.

[0020] In the backflow prevention joint of the present invention, the valve pipe may be divided into a fixed part having an inlet opening and a connection port, and an attachment part having a connected port connected to the connection port and an outlet opening, and the attachment part may be configured so as to be detachably attached to the fixed part by inserting and removing it in the vertical direction.

[0021] According to the present invention, by dividing the valve pipe into a fixed part and an attachment part, it becomes possible to easily remove the attachment part, which constitutes part of the valve pipe, and the valve body supported by the attachment part, from the fixed part while leaving the fixed part attached to the inlet of a drainage manhole, etc., thereby improving maintenance such as inspection and replacement of the valve body, etc. Effect of the Invention

[0022] According to the backflow prevention fitting of the present invention, an anti-adhesion cover is provided to cover the upper part of the rotating part such as a hinge for rotating the valve body, thereby preventing foreign matter such as filth contained in the wastewater from adhering to or accumulating on the rotating part such as the hinge, and preventing the movement of the valve body from being hindered by adhering matter.

[0023] According to the backflow prevention system of the present invention, the outflow outlet is positioned perpendicular to the inflow inlet so that wastewater that passes through the backflow prevention joint in a substantially horizontal direction falls freely under its own weight when it flows out of the outlet opening of the backflow prevention joint. This makes it possible to significantly reduce the amount of wastewater that bounces back into the backflow prevention joint directly or by colliding with a wall surface, etc., even when the amount of wastewater is large, and significantly reduces the risk of foreign matter contained in the wastewater adhering to the hinge portion, etc. [Brief description of the drawings]

[0024] [Figure 1] 1 is a perspective view showing an overall outline of a backflow prevention joint according to one embodiment of the present invention; [Diagram 2] 2 is a perspective view showing a valve body of the backflow prevention joint shown in FIG. 1. [Diagram 3] 2 is a perspective view showing a valve pipe of the check joint shown in FIG. 1. [Figure 4]4 is a perspective view showing a mounting portion of the valve pipe shown in FIG. 3. FIG. [Diagram 5] 4 is a perspective view showing a fixed portion of the valve pipe shown in FIG. 3. FIG. [Figure 6] 2 is a perspective view showing an adhesion prevention cover of the backflow prevention joint shown in FIG. 1. [Figure 7] 2 is a partial cross-sectional view showing a schematic diagram of the movement of a valve body in the backflow prevention joint shown in FIG. 1. [Figure 8] 1 is a perspective view showing an overall outline of a backflow prevention system (partially transparent) according to one embodiment of the present invention. [Figure 9] 9 is a cross-sectional view of the backflow prevention system shown in FIG. 8 taken along line XX. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] Hereinafter, a backflow prevention joint 1 according to one embodiment of the present invention and a backflow prevention system 2 to which the joint 1 is attached will be described in detail with reference to the drawings. Note that the present invention is not limited to the examples shown below, and various modifications are possible within the scope of the technical concept of the present invention. EXAMPLES

[0026] <Backflow prevention joint> Fig. 1 shows a perspective view illustrating an overall outline of a backflow prevention joint 1 according to one embodiment of the present invention. Of the backflow prevention joint 1 shown in Fig. 1, Fig. 2 shows a perspective view illustrating a valve body 3, Fig. 3 shows a perspective view illustrating a valve pipe 4, and Fig. 6 shows a perspective view illustrating an adhesion prevention cover 7. Also, of the valve pipe 4 shown in Fig. 3, Fig. 4 shows a perspective view illustrating an attachment part 5, and Fig. 5 shows a perspective view illustrating a fixing part 6.

[0027] As shown in Fig. 1, the backflow prevention joint 1 of this embodiment comprises a cylindrical valve pipe 4 (Fig. 3), a valve body 3 (Fig. 2) rotatably supported on the valve pipe 4, and an adhesion prevention cover 7 (Fig. 6) attached to the valve pipe 4 so as to cover the rotating part of the valve body 3. In this embodiment, the backflow prevention joint 1 is made of polyvinyl chloride resin, but there is no particular limitation on the material used, and known materials such as plastics can be used.

[0028] <Valve body> 2, the valve body 3 has a disk shape, and a hinge portion 30 is formed on the upper peripheral edge of the valve body 3. In order to reinforce the connection between the valve body 3 and the hinge portion 30 and to make it easier to break solid objects such as dirt that fall on the hinge portion 30 by cutting them, a plate-like rib 31 is formed on the outer periphery of the hinge portion 30, which extends further outward.

[0029] Figure 8 shows an oblique view illustrating an overall overview of a backflow prevention system 2 (partially transparent) according to one embodiment of the present invention, which is equipped with a backflow prevention fitting 1 of this embodiment, and Figure 9 shows a cross-sectional view of the backflow prevention system 2 shown in Figure 8 along line XX.

[0030] The valve body 3 has a flat downstream surface 32 and an upstream back surface 33 bulging from the downstream side to the upstream side, and is formed by joining the peripheral edge of the downstream surface 32 member and the peripheral edge of the upstream back surface 33 member in a liquid-tight manner (see FIG. 9). In addition, a packing 35 made of an elastic material such as rubber is attached to the peripheral edge of the valve body 3 at a position where it abuts against the valve seat portion 51, improving the sealing performance when the valve body 3 is closed.

[0031] Since the upstream back surface 33 of the valve body 3, which bulges toward the upstream side, functions in the same way as a streamlined shape, it does not receive a large force even when wastewater collides with the upstream back surface 33, but on the other hand, when the wastewater collides with the flat downstream surface 32, it becomes resisted and receives a large force. Therefore, in the backflow prevention joint 1 of this embodiment, when backflow occurs, the backflow water mainly collides with the downstream surface 32 of the valve body 3, so the valve body 3 receives a large force and operates to the closing side, thereby reliably preventing the backflow of wastewater.

[0032] In this embodiment, a space 34 is formed between the downstream surface 32 and the upstream back surface 33 of the valve body 3 (see FIG. 9). When a backflow occurs, the valve body 3 generates buoyancy in the space 34 when it is immersed in the backflowing water, so that the valve body 3 can stably maintain the closed state in contact with the valve seat portion 51, and can reliably prevent the backflow of wastewater.

[0033] 9, the point O of buoyancy generation in the space 34 of the valve disc 3 is disposed so as to be located upstream of the vertical plane passing through the rotation axis P of the valve disc 3. Therefore, when the valve disc 3 is immersed in backflowing water during the occurrence of a backflow, a moment acts on the valve disc 3 due to buoyancy to rotate it so as to close the outlet opening 50 of the valve pipe 4, preventing the valve disc 3 from malfunctioning by rotating to the opening side.

[0034] <Valve pipe> As shown in FIG. 3, the valve pipe 4 has a substantially circular inlet opening 60 for connection to an inlet of a catch basin or an outlet of a pipe (neither of which are shown), and a substantially circular outlet opening 50 that communicates with the inlet opening 60 and forms a valve seat portion 51 that abuts against the valve body 3.

[0035] In this embodiment, the outlet opening 50 (valve seat portion 51) is formed so as to incline from the downstream side to the upstream side as it goes from top to bottom (see FIG. 9).

[0036] Therefore, under normal circumstances, the valve body 3, which is suspended by its own weight, opens the outlet opening 50 of the valve pipe 4 and can allow a small amount of forward flow wastewater to flow, effectively preventing clogging due to foreign matter contained in the wastewater. In addition, in the backflow prevention system 2 in which the backflow prevention joint 1 of this embodiment is attached to the inlet 80 of the T-shaped cylindrical body 8, which will be described later, the wastewater flowing out from the outlet opening 50 falls freely downward by its own weight, so that even when the amount of wastewater is large, the amount of wastewater that bounces back onto the rotating part of the valve body 3 directly or by colliding with a wall surface or the like can be significantly reduced, and the risk of foreign matter contained in the wastewater adhering to the rotating part can be significantly reduced.

[0037] In this embodiment, the valve pipe 4 is divided into a fixed part 6 (FIG. 5) having an inlet opening 60 and a connection port 61 communicating with the inlet opening 60 and semi-permanently attached to a catch basin inlet or a piping outlet (neither of which are shown), and an attachment part 5 (FIG. 4) having a connected port 52 detachably connected to the connection port 61 and an outlet opening 50 communicating with the connected port 52. The connected port 52 is configured to be connected in alignment with the connection port 61 when the attachment part 5 is attached to the fixed part 6, and in order to make the connection between them even more liquid-tight, a packing (not shown) made of an elastic material such as rubber can be attached to the open end of the connection port 61 or the open end of the connected port 52.

[0038] At both left and right ends of the connection port 61 of the fixed part 6, hook parts 62 are formed with their tips bent toward each other and extending vertically, and at both left and right ends of the connected port 52 of the mounting part 5, fitting parts 53 are formed extending vertically and fitting into the hook parts 62 by inserting them from above. Also, at the top of the mounting part 5, a tower-shaped handle part 54 is formed that can be grasped by hand or hung using a dedicated jig or the like.

[0039] Therefore, in this embodiment, by inserting and removing the mounting part 5 in the vertical direction while leaving the fixing part 6 attached to the inlet of a drainage manhole, etc., it is possible to easily attach or remove the mounting part 5 and the valve body 3 journaled on the mounting part 5, thereby improving maintenance such as inspection, cleaning, and replacement of the valve body 3, etc.

[0040] 1 and 3, a hinge support part 55 for rotatably supporting the hinge part 30 of the valve body 3 is provided on the upper part of the mounting part 5 (valve pipe 4). There is no particular limitation on the shape or number of the hinge support parts 55, but in this embodiment, the hinge support part 55 is arranged on the side of the hinge part 30 so that the shaft hole of the hinge support part 55 aligns with the shaft hole of the hinge part 30, and a pin 56 is inserted into each shaft hole to rotatably support the valve body 3.

[0041] The configuration of the hinge portion 30 and the hinge support portion 55 may be such that, as in this embodiment, a pair of hinge support portions 55 are provided on the valve tube 4 so as to sandwich one hinge portion 30 of the valve body 3 from both sides, or, although not shown, a pair of hinge portions may be provided on the valve body so as to sandwich one hinge portion support portion of the valve tube from both sides. In order to achieve uniform rotation of the force applied to the pin 56, it is preferable to have at least two or more of either the hinge portions or the hinge support portions.

[0042] <Adhesion prevention cover> Figure 6 shows an oblique view illustrating the anti-adhesion cover 7 of the backflow prevention fitting 1 shown in Figure 1, and Figure 7 shows a partial cross-sectional view diagrammatically illustrating the movement of the valve body 3 in the backflow prevention fitting 1 shown in Figure 1.

[0043] As shown in Figures 1 and 9, the backflow prevention fitting 1 of this embodiment has an anti-adhesion cover 7 attached to the upper part of the hinge portion 30 of the valve body 3 and the hinge support portion 55 of the valve pipe 4 (mounting portion 5) so as to cover all or part of the hinge portion 30 and the hinge support portion 55.

[0044] Therefore, in the backflow prevention fitting 1 of this embodiment, foreign matter such as filth contained in the wastewater is prevented from adhering to or accumulating on rotating parts such as the hinge portion 30 used to rotate the valve body 3, and the movement of the valve body 3 is not hindered by adhesions or solidification of the adhesions.

[0045] There are no particular limitations on the shape of the adhesion prevention cover 7, so long as it can prevent foreign matter, such as dirt contained in the wastewater, from scattering or adhering to the rotating part of the valve body 3. In this embodiment, as shown in Fig. 6, the adhesion prevention cover 7 is composed of a stopper portion 70 bent in an L-shape, and a clamp portion 71 connected to support the stopper portion 70.

[0046] The stopper portion 70 is disposed above the rib 31 of the hinge portion 30 of the valve body 3 at a position spaced from the rib 31 so as to cover the hinge portion 30 and the rib 31. The clamp portion 71 is disposed so as to cover at least the upper portion of the contact portion between the hinge portion 30 and the hinge support portion 55 and the upper portion of the hinge support portion 55, and in this embodiment, the clamp portion 71 is further extended to the axially outer side of the hinge support portion 55 to strengthen the prevention of adhesion due to scattering of foreign matter contained in the wastewater.

[0047] Moreover, the clamp portion 71 is made of an elastic resin material and can detachably clamp the outer circumference of the hinge support portion 55. Therefore, in this embodiment, the adhesion prevention cover 7 is detachably attached to the hinge support portion 55 of the valve pipe 4 by the clamp portion 71, so that the adhesion prevention cover 7, which is easily soiled, can be easily removed from the system for cleaning. In this embodiment, the clamp portion 71 has a folded portion 72 extending in a direction away from the hinge support portion 55, so that the adhesion prevention area is further expanded and the adhesion prevention cover 7 can be easily attached and detached by pinching the folded portion 72. Note that the adhesion prevention cover 7 does not necessarily need to be supported by the hinge support portion 55, and may be directly or indirectly attached to the valve pipe 4 as long as it can cover all or part of the hinge portion 30 and the hinge support portion 55.

[0048] Figure 7 shows a partial cross-sectional view that shows a schematic representation of the movement of the valve disc 3 in the backflow prevention joint 1 shown in Figure 1. In Figure 7, the valve disc 3 when suspended by its own weight is shown by a solid line, and the valve disc 3 when at the limit of its rotation on the opening side due to the rib 31 of the hinge portion 30 abutting against the adhesion prevention cover 7 is shown by a two-dot chain line.

[0049] As can be understood by referring to Fig. 7, in the backflow prevention joint 1 of this embodiment, the adhesion prevention cover 7 also functions as a stopper that restricts the rotation range of the valve body 3. More specifically, when the valve body 3 rotates to the opening side by a predetermined angle, the adhesion prevention cover 7 is disposed at a position where the hinge portion 30 (rib 31) abuts, thereby restricting the rotation range of the valve body 3. In this embodiment, the downstream end of the adhesion prevention cover 7 not only comes into point contact with the rib 31, but also the lower abutment surface of the adhesion prevention cover 7 is made similar in shape to the outer shape of the rib 31 so that the entire lower abutment surface of the adhesion prevention cover 7 comes into line contact with the rib 31, thereby preventing localized uneven wear.

[0050] In this embodiment, since the adhesion prevention cover 7 also functions as a stopper, it is preferable to arrange the adhesion prevention cover 7 so that at least the downstream end portion is separated from the hinge portion 30 (rib 31) in the valve body 3 that is suspended by its own weight when there is no drainage or the drainage amount is small and the drainage pressure acting by colliding with the valve body 3 is unloaded. Note that the portion of the valve body 3 that comes into contact with the adhesion prevention cover 7 does not necessarily have to be the rib 31, and may be, for example, the hinge portion 30 or the valve body 3 itself, as long as it is a portion that can regulate the rotation range of the valve body 3.

[0051] In the backflow prevention joint 1, if the rotation range of the valve element 3 to the opening side becomes too large, backflow water may collide with the upstream back surface 33 of the valve element 3 when a backflow occurs, and the valve element 3 may not be able to operate to the closing side. However, according to the backflow prevention joint 1 of this embodiment, the adhesion prevention cover 7 functions as a stopper that restricts the rotation range of the valve element 3, so that backflow water is guaranteed to collide with the downstream surface 32 of the valve element 3, and the valve element 3 is guaranteed to rotate to the closing side without malfunctioning due to backflow water.

[0052] In this embodiment, in order to ensure proper flow of forward flow drainage and to reliably prevent the flow of backflow water, the outlet opening 50 (valve seat portion 51) of the valve pipe 4 is formed at an angle (α) of 20° toward the upstream side from the vertical direction, and the rotation angle (θ) of the valve body 3 toward the opening side by the adhesion prevention cover 7 is preferably set to approximately 60° (rotation angle (β) of 40° toward the downstream side from the vertical direction) from the outlet opening 50 (valve seat portion 51), more preferably approximately 45° (rotation angle (β) of 25° toward the downstream side from the vertical direction) (see Figure 7).

[0053] <Backflow prevention system> As shown in FIGS. 8 and 9, the backflow prevention system 2 of this embodiment can be constructed by attaching the above-mentioned backflow prevention joint 1 of the present invention to the inlet 80 of a T-shaped cylindrical body 8.

[0054] More specifically, the T-shaped cylindrical body 8 used in the backflow prevention system 2 of this embodiment is generally called a two-way T-shaped tube, and has an inlet 80 that opens horizontally, an outlet 81 that communicates with the inlet 80 and opens downward, and an inspection hatch 82 that communicates with the inlet 80 and the outlet 81 and opens upward. In this embodiment, the inlet 80, the outlet 81 and the inspection hatch 82 all have a socket shape, and inside each of the sockets 80, 81, 82 there is formed a step 83 against which the tip of a connecting pipe (not shown) can abut.

[0055] Therefore, in the backflow prevention system 2 of this embodiment, the backflow prevention fitting 1 of the present invention is attached by inserting the inlet opening 60 of the backflow prevention fitting 1 into the outlet 81 from the outside of the cylindrical body 8, and even when the forward flow drainage volume is large, the backflow prevention fitting 1 will not fall out of the outlet 81.

[0056] As shown in Figures 8 and 9, the backflow prevention system 2 of this embodiment can adjust the diameter of the outlet 81 appropriately to match the piping diameter of the connecting pipe connected to the outlet 81 by attaching a different diameter socket 9 to the outlet 81 of a T-shaped cylindrical body 8, the different diameter socket 9 having an outer peripheral portion having an outer diameter the same as the inner diameter of the outlet 81 and an inner peripheral portion having an inner diameter smaller than the outer diameter of the outer peripheral portion.

[0057] According to the backflow prevention system 2 of this embodiment, the outlet 81 is arranged perpendicular to the inlet 80 so that the wastewater that passes through the backflow prevention joint 1 in an approximately horizontal direction falls freely under its own weight when it flows out of the outlet opening 50 of the backflow prevention joint 1.This makes it possible to significantly reduce the amount of wastewater that bounces back into the backflow prevention joint 1 directly or by colliding with a wall surface, etc., even when the amount of wastewater is large, and significantly reduces the risk of foreign matter contained in the wastewater adhering to rotating parts such as the hinge portion 30 of the valve body 3.

[0058] In this embodiment, both the T-shaped cylindrical body 8 and the different diameter socket 9 are made of polyvinyl chloride resin, but there is no particular limitation on the material used, and known materials such as plastics can be used. [Explanation of symbols]

[0059] 1. Backflow prevention joint 2. Backflow prevention system 3. Valve body 30 Hinge part 31 Rib 32...Downstream surface 33...Upstream side back 34...space 35... Packing 4. Valve pipe 5. Mounting part 50...Exit opening 51 Valve seat 52 Connection port 53 Fitting part 54...Handle part 55 Hinge support part 56···pin 6... Fixed part 60...Inlet opening 61 Connection port 62...Hook part 7. Anti-adhesion cover 70 Stopper part 71 Clamp section 72... Folded part 8. T-shaped cylindrical body 80...Inlet 81...outlet 82 Inspection hatch 83. Step 9. Different diameter socket O: Point where buoyancy occurs P Rotation axis α: Incline angle of the valve pipe outlet opening (valve seat) β: Rotation angle of the valve disc from the vertical direction θ: Rotation angle of the valve disc

Claims

1. A valve body, a valve pipe having an inlet opening and an outlet opening forming a valve seat portion that abuts against the valve body; A hinge portion provided on the peripheral edge of the valve body; and a hinge support portion disposed on a side of the hinge portion to rotatably support the hinge portion and provided on an upper portion of the valve pipe; In a backflow prevention joint comprising: A backflow prevention joint, characterized in that it is provided with an anti-adhesion cover arranged on top of the hinge portion and the hinge support portion so as to cover all or part of the hinge portion and the hinge support portion.

2. 2. The backflow prevention joint according to claim 1, wherein the adhesion prevention cover is removably attached to the hinge support portion.

3. 3. The backflow prevention joint according to claim 2, wherein the adhesion prevention cover has a clamp portion that clamps the outer periphery of the hinge support portion.

4. 2. The backflow prevention joint according to claim 1, wherein the adhesion prevention cover restricts the rotation range of the valve body by abutting against the hinge portion.

5. The backflow prevention joint according to claim 4, wherein, when no load is applied, the downstream end of the adhesion prevention cover is positioned away from the hinge portion.

6. 2. The backflow prevention joint according to claim 1, wherein the valve body has a downstream surface that is flat and an upstream back surface that is bulged upstream.

7. 7. The backflow prevention joint according to claim 6, wherein a space is formed between the downstream side surface and the upstream side back surface of the valve body.

8. the valve pipe is divided into a fixed portion having the inlet opening and a connection port, and an attachment portion having a connected port connected to the connection port and the outlet opening, and The backflow prevention joint according to claim 1, wherein the mounting portion is detachably attached to the fixing portion by being inserted and removed in an up-down direction.

9. An inlet opening in a horizontal direction; an outlet port communicating with the inlet port and opening downward; and an inspection hatch communicating with the inlet and the outlet and opening upward; In a T-shaped cylindrical body having A backflow prevention system, comprising a backflow prevention joint according to any one of claims 1 to 8 attached to the inlet.

10. The backflow prevention system of claim 9, further comprising a differential diameter socket at the outlet, the differential diameter socket having an outer periphery having an outer diameter the same as the inner diameter of the outlet, and an inner periphery having an inner diameter smaller than the outer diameter of the outer periphery.

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