JP7631162B2 - Backflow prevention fitting - Google Patents

Description

The present invention relates to a backflow prevention joint that is attached to the inlet/outlet of drainage facilities such as manholes, public manholes, and drainage manholes, and the drainage outlet of a waterway, and in particular to a backflow prevention joint equipped with a float means that assists and ensures the opening and closing action of a valve body via a link means.

In general, 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.

However, due to abnormal weather in recent years, there have been frequent cases of large amounts of rainwater flowing into the main sewer pipes in a short period of time. This causes the drainage capacity of the main sewer pipes to be exceeded, resulting in the overflow of wastewater backing up through catch basins, etc., and causing the backflow to gush out from indoor drainage equipment connected to the drain pipes.

For this reason, in order to prevent wastewater that has backed up from the sewer main pipe from passing through a drainage manhole or the like and overflowing from indoor drainage equipment, backflow prevention valves have been developed that are attached to the inlet of a drainage manhole, as described in, for example, JP 2020-153508 A (Patent Document 1), JP 2018-204198 A (Patent Document 2), and JP 2010-248904 A (Patent Document 3).

The check valve described in Patent Document 1 tilts the valve seat surface of the valve pipe outlet forward to provide a gap between the valve body and the valve seat surface under normal conditions, ensuring a smooth drainage flow, and when the water level rises, the valve body is pressed from the front by backflow water, causing it to rotate backward and come into contact with the valve seat surface, preventing drainage water from backflowing upstream. In addition to the configuration of the check valve in Patent Document 1, the check valve described in Patent Document 2 configures all or part of the valve body as a buoyancy generating part, making it possible to more reliably open and close the valve body under normal conditions and when backflow occurs.

However, in the check valves described in Patent Documents 1 and 2, the valve element is merely suspended so as to be able to swing freely at the valve pipe outlet. In particular, when a large amount of rainwater flows into a drainage basin or the like all at once due to a typhoon or torrential rain, the flow of drainage water accompanied by violent waves and the pressure change inside the drainage basin due to backflow water will cause the valve element to repeatedly swing unstably between the side that closes and the side that opens the valve pipe outlet. For this reason, in the check valves described in Patent Documents 1 and 2, if rainwater flows into the drainage basin or the like at the time when the valve element swings to the side that opens the valve pipe outlet, the buoyancy of the valve element will have an adverse effect, and the valve element will be unable to return to the closing direction while keeping the valve pipe outlet open, and there is a problem in that it will be impossible to prevent the drainage water from flowing back upstream.

The check valve described in Patent Document 3 has an end face of the valve seat that is inclined from the upstream side to the downstream side as it moves from the top to the bottom, so that under normal circumstances the valve body abuts against the valve seat, but the valve body is lifted by the forward flow of drainage water to ensure the flow of said drainage water, and in an emergency, the valve body maintains its abutment against the valve seat to prevent the flow of reverse drainage water.

In other words, the check valve described in Patent Document 3 is intended to prioritize preventing backflow water that occurs temporarily due to a sudden downpour from flowing back upstream, rather than ensuring the normal flow of forward-flow drainage. Therefore, even under normal circumstances, a small amount of forward-flow drainage flow cannot reliably open the valve body, causing instability (leading to drainage blockages).

In addition, a flap gate, such as that described in Utility Model Registration No. 3200989 (Patent Document 4), is known as an example of a device that more reliably opens and closes the valve body during normal and reverse flow conditions by providing a buoyancy generating unit separate from the valve body.

However, in the flap gate described in Patent Document 4, the gate body is suspended so as to be able to swing freely at the outlet of the waterway, and the float mechanism that assists in the opening and closing of the gate body is in contact with the gate body via a roller attached to the tip of the float lever so as not to restrict the movement of the gate body, and is not connected to it. For this reason, even in the flap gate described in Patent Document 4, if rainwater flows back when the gate body swings in the direction opening the outlet of the waterway, the gate body detaches from the float mechanism and is unable to return to the closing direction while leaving the outlet of the waterway open, which results in the problem that it is no longer possible to prevent wastewater from flowing back upstream.

JP 2020-153508 A JP 2018-204198 A JP 2010-248904 A Utility Model Registration No. 3200989

The present invention aims to provide a backflow prevention valve that can be attached to the inlet/outlet of drainage facilities such as manholes, public inlets, and drainage manholes, or the outlet of a waterway, and that ensures smooth forward flow drainage by reliably operating the valve body to open the valve pipe under normal circumstances, and yet, even in an emergency in which a large amount of rainwater flows into a drainage manhole or the like all at once, the valve body reliably operates to close the valve pipe, preventing drainage water from flowing back upstream.

The inventors have conducted extensive research into the pivoting mechanism of valve bodies and mechanisms and structures for supporting the pivoting mechanism of check valves and flap gates that are attached to the inlets/outlets of drainage equipment such as catch basins and the drainage outlets of waterways. As a result, they have discovered that the above problems can be solved by providing a buoyancy generating part that rises and falls according to the height of the liquid level separately from the valve body attached to open and close the outlet of the valve tube, and connecting linking means between the valve tube and the valve body that rotates the valve body to close the outlet of the valve tube as the buoyancy generating part rises, and rotates the valve body to open the outlet of the valve tube as the buoyancy generating part descends, thereby completing the present invention.

In other words, according to the present invention, a backflow prevention joint is provided that includes a valve pipe having an inlet and an outlet, a valve body rotatably attached to the valve pipe so as to open and close the outlet of the valve pipe, link means having one end rotatably attached to the valve pipe and the other end rotatably attached to the valve body, and a buoyancy generating part attached to the link means and that rises and falls according to the height of the liquid level, wherein the link means rotates the valve body to close the outlet of the valve pipe as the buoyancy generating part rises, and rotates the valve body to open the outlet of the valve pipe as the buoyancy generating part descends.

In addition, in the present invention, it is preferable that one end of the linking means is rotatably attached to the valve tube at a fulcrum that is different from the fulcrum about which the valve body rotates, and further, it is preferable that the linking means is composed of at least two connecting arms, a first connecting arm having one end and a second connecting arm that is rotatably connected to the first connecting arm and has the other end.

In this way, in the backflow prevention joint of the present invention, the buoyancy generating part, which is provided separately from the valve body of the check valve, rises and falls according to the height of the liquid level of the backflowing wastewater. A link means is connected between the valve pipe and the valve body, which rotates the valve body to close the outlet of the valve pipe as the buoyancy generating part rises, and rotates the valve body to open the outlet of the valve pipe as the buoyancy generating part descends.

Therefore, even in a situation where a large amount of rainwater flows back at once and around the opening side (upstream) of the valve body, the buoyancy generating part, which is raised by the backflowing water, reliably operates the valve body in the closing direction via the link means, so that the backflowing water can be reliably prevented from flowing further upstream. Also, under normal circumstances, a moment acts in the direction of opening the valve body due to the weight of the buoyancy generating part at the fulcrum of the valve pipe that supports the valve body, so that the valve body is not obstructed and a smooth forward flow of drainage can be guaranteed.

The backflow prevention joint of the present invention can be attached to the inlet/outlet of drainage facilities such as manholes, public manholes, and drainage manholes, or the drainage outlet of a waterway. In particular, by providing a guide arm that extends in a direction different from the direction in which the valve body extends, sandwiching the fulcrum around which the valve body rotates in a side view, and by rotatably connecting a second connecting arm to the guide arm, the ascending and descending movement of the buoyancy generating part can be efficiently converted into the opening and closing movement of the valve body.

In this case, it is preferable that the buoyancy generating part is located downstream of the fulcrum around which the valve body rotates. In addition, since this type of backflow prevention joint requires an operating space for the buoyancy generating part to be provided downstream of the valve body, it is suitable for installation at the inlet of drainage facilities such as manholes, public manholes, and drainage manholes, or the outlet of waterways.

In the above type of backflow prevention joint, in order to increase the force generated by the upward and downward movement of the buoyancy generating part and transmit it to the valve body via the second connecting arm and the second connecting arm, it is effective to provide an extension arm on the buoyancy generating part and attach the buoyancy generating part to the second connecting arm via the extension arm.

In addition, in the backflow prevention joint of the present invention, the second connecting arm is rotatably connected to the valve body at a fulcrum that is different from the fulcrum around which the valve body rotates in a side view, so that the ascending and descending movement of the buoyancy generating part can be efficiently converted into the opening and closing movement of the valve body.

In this case, it is preferable that the buoyancy generating part is located upstream of the fulcrum around which the valve body rotates. In addition, since this type of backflow prevention coupling requires an operating space for the buoyancy generating part to be provided upstream of the valve body, it is suitable for installation at the outlet of drainage facilities such as manholes, public manholes, and drainage manholes.

In the above type of backflow prevention joint in which the buoyancy generating part is located upstream of the valve body, in order to increase the force generated by the upward and downward movement of the buoyancy generating part and transmit it to the valve body via the first connecting arm and the second connecting arm, it is effective to provide an extension arm on the buoyancy generating part and attach the buoyancy generating part to the first connecting arm via the extension arm.

In either type where the buoyancy generating unit is located downstream or upstream of the valve disc, it is preferable that the buoyancy generating unit has a specific gravity smaller than that of water to ensure the upward movement of the buoyancy generating unit due to backflow water. Also, in order for the valve disc to normally keep the outlet of the valve pipe open, it is preferable to set the moment acting in the direction of opening the valve disc due to the weight of the buoyancy generating unit at the fulcrum of the valve pipe that supports the valve disc so that it is greater than the moment acting in the direction of closing the valve disc due to the weight of the valve disc.

In addition, in order to ensure the flow of wastewater under normal circumstances by forming a gap between the valve body and the valve pipe outlet, and to prevent backflow of wastewater by closing the valve body only when the water level rises, it is preferable to form the outlet of the valve pipe so that its end face slopes from downstream to upstream as it moves from the top to the bottom.

According to the present invention, there is provided a backflow prevention joint comprising a valve pipe having an inlet and an outlet, a valve body rotatably attached to the valve pipe so as to open and close the outlet of the valve pipe, link means having one end rotatably attached to the valve pipe and the other end rotatably attached to the valve body, and a buoyancy generating part attached to the link means and rising and falling according to the height of the liquid level, characterized in that the link means rotates the valve body to close the outlet of the valve pipe as the buoyancy generating part rises, and rotates the valve body to open the outlet of the valve pipe as the buoyancy generating part descends.

In this way, in the backflow prevention joint of the present invention, the buoyancy generating part, which is provided separately from the valve body of the check valve, rises and falls according to the height of the liquid level of the backflowing wastewater. A link means is connected between the valve pipe and the valve body, which rotates the valve body to close the outlet of the valve pipe as the buoyancy generating part rises, and rotates the valve body to open the outlet of the valve pipe as the buoyancy generating part descends.

Therefore, even in a situation where a large amount of rainwater flows back at once and around the opening side (upstream) of the valve body, the buoyancy generating part, which is raised by the backflowing water, reliably operates the valve body in the closing direction via the link means, so that the backflowing water can be reliably prevented from flowing further upstream. Also, under normal circumstances, a moment acts in the direction of opening the valve body due to the weight of the buoyancy generating part at the fulcrum of the valve pipe that supports the valve body, so that the valve body is not obstructed and a smooth forward flow of drainage can be guaranteed.

1 is a perspective view showing an entire backflow prevention joint according to one embodiment of the present invention; 2 is a side view showing a state in which a valve body opens a valve pipe in the backflow prevention joint shown in FIG. 1. FIG. 3 is a cross-sectional view of the backflow prevention joint shown in FIG. 2 taken along a cross section passing through the central axis of the valve pipe. 2 is a side view showing the backflow prevention joint shown in FIG. 1 in a state where a valve body closes a valve pipe. 5 is a cross-sectional view of the backflow prevention joint shown in FIG. 4 taken along a cross section passing through the central axis of the valve pipe. 2 is a cross-sectional view of a drainage manhole showing an embodiment in which the backflow prevention joint shown in FIG. 1 is attached to the manhole. FIG. 11 is a perspective view showing the entire backflow prevention joint according to another embodiment of the present invention. 8 is a side view showing a state in which the valve body opens the valve pipe in the backflow prevention joint shown in FIG. 7. FIG. 9 is a cross-sectional view of the backflow prevention joint shown in FIG. 8 taken along a cross section passing through the central axis of the valve pipe. 8 is a side view showing the backflow prevention joint shown in FIG. 7 in a state where the valve body closes the valve pipe. FIG. 11 is a cross-sectional view of the backflow prevention joint shown in FIG. 10 taken along a cross section passing through the central axis of the valve pipe. 8 is a cross-sectional view of a drainage manhole showing the backflow prevention joint shown in FIG. 7 attached to the manhole.

The following describes in detail a backflow prevention joint according to one embodiment of the present invention 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.

First Embodiment
FIG. 1 is a perspective view showing an entire backflow prevention joint 1 according to a first embodiment of the present invention.

As shown in FIG. 1, the backflow prevention joint 1 of the first embodiment includes a valve pipe 2 having an inlet 20 and an outlet 21, a valve body 3 rotatably attached to the valve pipe 2 so as to open and close the outlet 21 of the valve pipe 2, and a buoyancy generating part 4 that rises and falls according to the height of the liquid surface. In addition, between the valve pipe 2 and the valve body 3, a link means 5 is attached, which is composed of a first connecting arm 50 having a first end 500 rotatably attached to the valve pipe 2, and a second connecting arm 51 rotatably connected to the first connecting arm 50 and having a second end 510 rotatably attached to the valve body 3.

In the backflow prevention joint 1 of the first embodiment, the link means 5 consisting of the first connecting arm 50 and the second connecting arm 51 functions to rotate the valve body 3 to close the outlet 21 of the valve pipe 2 as the buoyancy generating part 4 rises, and to rotate the valve body 3 to open the outlet 21 of the valve pipe 2 as the buoyancy generating part 4 descends.

Figure 2 shows a side view of the backflow prevention joint 1 shown in Figure 1 when the valve body 3 opens the valve pipe 2, and Figure 3 shows a cross-sectional view of the backflow prevention joint 1 shown in Figure 2 taken along a cross section passing through the central axis of the valve pipe 2. Figure 4 shows a side view of the backflow prevention joint 1 shown in Figure 1 when the valve body 3 closes the valve pipe 2, and Figure 5 shows a cross-sectional view of the backflow prevention joint 1 shown in Figure 4 taken along a cross section passing through the central axis of the valve pipe 2.

<Valve pipe>
In the backflow prevention joint 1 of the first embodiment, polyvinyl chloride resin is used as the material of the valve pipe 2, but there is no particular limitation on the material used, and known materials such as plastics can be used. In addition, the valve pipe 2 is configured as a short straight pipe with a circular cross section, but it does not necessarily have to be entirely straight and may include a curved pipe section. In addition, the diameter of the valve pipe 2 does not necessarily have to be uniform, and it may be configured as a differential diameter pipe joint in which the diameters of the inlet 20 and the outlet 21 are different, for example.

In the first embodiment, the outlet 21 of the valve pipe 2 is formed so that its end face (valve seat surface) slopes from downstream to upstream as it moves from the top to the bottom. Therefore, in the backflow prevention joint 1, a gap is formed between the valve body 3 and the outlet 21 of the valve pipe 2 under normal conditions, ensuring a smooth flow of forward flow drainage, and only when the water level rises does the valve body 3 close the outlet 21 to prevent drainage from flowing back.

However, in the first embodiment, when the drainage surface has not reached the buoyancy generating section 4, a moment acts on the valve body 3 in a direction to open the valve body 3 due to the weight of the buoyancy generating section 4 (Figs. 2 and 3), so the end face (valve seat surface) of the outlet 21 of the valve pipe 2 does not necessarily need to be inclined as described above, and may be a vertical surface or a surface that inclines from the upstream side to the downstream side as it moves from the top to the bottom.

A pair of support arms 22 are formed above the outlet 21 of the valve pipe 2, and the pair of support arms 22 includes a fulcrum O for rotatably supporting the valve body 3 and a fulcrum P for rotatably supporting the first end 500 of the first connecting arm 50 of the link means 5 at a position different from the fulcrum O in a side view. The support arms 22 are not particularly limited in shape or attachment position, but in the first embodiment, they extend upward from the outer periphery of the valve pipe 2. Therefore, when the valve pipe 2 is inserted into the inlet 60 of the drainage basin 6 to attach the backflow prevention joint 1, the support arms 22 not only abut against the end face of the inlet 60 to function as a stopper (see FIG. 6), but also have the advantage that the fulcrum P can be placed at a position different from the fulcrum O within one member.

There are no particular limitations on the structure for rotatably supporting the valve body 3 and the first end 500 of the first connecting arm 50 at the fulcrum O and fulcrum P of the support arm 22, but in the first embodiment, the fulcrum O is structured to rotatably grasp the rotation shaft provided at the top of the valve body 3 from both sides with bearings formed on each of the pair of support arms 22, and the fulcrum P is structured to rotatably grasp the rotation shaft provided at the first end 500 of the first connecting arm 50 from both sides with bearings formed on each of the pair of support arms 22.

In addition, when the valve pipe 2 is inserted into the inlet 60 of the drainage manhole 6 to attach the backflow prevention joint 1 (Figure 6), a rubber annular valve pipe packing 23 is attached to the outer periphery of the valve pipe 2 to seal the gap between the outer periphery of the valve pipe 2 and the inner wall surface of the inlet 60. The valve pipe packing 23 is fixed in a circumferential groove 24 formed on the outer periphery of the valve pipe 2.

<Valve body>
In the backflow prevention joint 1 of the first embodiment, polyvinyl chloride resin is used as the material of the valve body 3, but the material to be used is not particularly limited, and known materials such as plastics can be mainly used. In addition, the shape of the valve body 3 may be any shape that can abut against the outlet 21 of the valve pipe 2 to completely block the outlet 21, and since the outlet 21 of the valve pipe 2 has a substantially circular shape in the first embodiment, the valve body 3 has a substantially circular shape in front view in accordance with the shape of the outlet 21. In addition, a valve body packing 32 is attached to the abutment surface of the valve body 3 that abuts against the end face (valve seat surface) of the outlet 21 of the valve pipe 2 to improve the sealing performance with the outlet 21 when the valve body 3 is closed, and the valve body packing 32 is fitted into a fitting groove 33 formed on the upstream surface 30 of the valve body 3.

As shown in Figures 2 and 4, the valve body 3 is provided with a guide arm 34 that extends in a direction different from the direction in which the valve body 3 extends, sandwiching the fulcrum O about which the valve body 3 rotates in a side view, in order to rotatably connect the second connecting arm 51 at the fulcrum Q. That is, in the above configuration, the guide arm 34 serves as a force point or point of action, and the valve body 3 serves as a force point or point of action utilizing the principle of leverage. Therefore, in the backflow prevention joint 1 of the first embodiment, by connecting the second connecting arm 51 to the guide arm 34, the upward and downward movement generated in the buoyancy generating section 4 can be efficiently converted into the opening and closing movement of the valve body 3.

As shown in Figures 3 and 5, the valve body 3 is formed with a curved downstream surface 31 that is concave from the downstream side toward the upstream side. Therefore, the valve body 3 receives a greater force (resistance) from reverse flow drainage that collides with the downstream surface 31 than from forward flow drainage that collides with the upstream surface 30. Therefore, when drainage water flows backward through the backflow prevention joint 1 to the upstream side, the valve body 3 reliably operates to close the outlet 21 of the valve pipe 2, and also prevents the valve body 3 from malfunctioning to open the outlet 21 of the valve pipe 2 due to the difference in resistance force generated on the front and back surfaces 30 and 31 of the valve body 3.

Although not shown, in the first embodiment, the valve body 3 may be buoyant. In the backflow prevention joint 1 of the first embodiment, the outlet 21 of the valve pipe 2 is formed so as to be inclined from the downstream side to the upstream side as it moves from the top to the bottom, so that when wastewater flows back into the backflow prevention joint 1, the valve body 3 operates to close the outlet 21 of the valve pipe 2 more easily and reliably.

There are no particular limitations on the means for imparting buoyancy to the valve body 3, but examples of configurations for imparting buoyancy include a method in which an enclosed space is provided between the upstream and downstream surfaces of the valve body, making the valve body a hollow structure, or a method in which a second buoyancy generator with a specific gravity smaller than that of water is provided on the downstream surface 31 of the valve body 3.

<Linking Method>
In the backflow prevention joint 1 of the first embodiment, the link means 5 is composed of a first connecting arm 50 having a first end 500 rotatably attached to the support arm 22 of the valve pipe 2 at a fulcrum P, and a second connecting arm 51 rotatably connected to the first connecting arm 50 at a fulcrum R and having a second end 510 rotatably attached to the guide arm 34 of the valve element 3 at a fulcrum Q. In other words, the link means 5 has one end rotatably attached to the valve pipe 2 at the fulcrum P, and the other end rotatably attached to the valve element 3 at the fulcrum Q.

The first connecting arm 50 and the second connecting arm 51 may have any shape or configuration as long as they do not interfere with each other's operation, and there are no particular limitations on their shape or configuration. In the first embodiment, the first connecting arm 50 has a rod-like shape with rotation axes formed at both ends (fulcrums P and R), and the second connecting arm 51 is composed of a pair of rod-like sub-arms 511, 512 so that the rotation axis at fulcrum R of the first connecting arm 50 and the rotation axis at fulcrum Q of the valve body 3 can be grasped from both sides by a pair of bearings.

In the first embodiment, polyvinyl chloride resin is used as the material for the first connecting arm 50 and the pair of rod-shaped sub-arms 511, 512, but there are no particular limitations on the material used, and known materials such as plastics can be used. In addition, in this specification, the "one end", "other end" and "end" of the link means 5 do not mean the end faces of the ends of the arms 50, 511, 512 in the strict sense, but rather mean the "one end", "other end" and "end" of the link means 5 on which a rotating shaft or bearing can be provided.

<Buoyancy generating part>
In the backflow prevention joint 1 of the first embodiment, the buoyancy generating part 4, which assists and ensures the opening and closing action of the valve body 3 so that the valve body 3 does not malfunction under normal or abnormal conditions, is non-rotatably attached to the second connecting arm 51 of the link means 5. Also, in the first embodiment, the buoyancy generating part 4 is attached to the second connecting arm 51 via a round bar-shaped extension arm 40 in order to increase the force generated by the rising and falling of the buoyancy generating part 4 and transmit it to the valve body 3 via the second connecting arm 51 and the second connecting arm 52.

The buoyancy generating unit 4 is not particularly limited in shape, structure, material, etc., as long as it has a specific gravity smaller than that of water so as to generate buoyancy against backflowing water. In the first embodiment, the buoyancy generating unit 4 is made of a plastic hollow structure, which has low resistance against backflowing water and is easy to manufacture, and the plastic is preferably polyvinyl chloride resin, and the hollow structure is preferably a hollow sphere. In addition, in order to ensure that the valve body 3 opens the outlet 21 of the valve pipe 2 under normal conditions, the weight of the buoyancy generating unit 4 is set so that the moment acting in the direction of opening the valve body 3 due to the weight of the buoyancy generating unit 4 is greater than the moment acting in the direction of closing the valve body 3 due to the weight of the valve body 3 at the fulcrum O of the valve pipe 2 supporting the valve body 3.

Figure 6 shows a cross-sectional view of the drainage manhole 6, showing how the backflow prevention joint 1 shown in Figure 1 is attached to the manhole 6.

The drainage manhole 6 shown in FIG. 6 is a partially enlarged lower portion of a typical drainage manhole 6, and includes an inlet 60, an outlet 61, and an inverted portion 62 connecting the inlet 60 and the outlet 61, and an opening 63 is provided above the inverted portion 62 for connecting a riser pipe (not shown) having an inspection port. In the first embodiment, the drainage manhole 6 is entirely molded from polyvinyl chloride resin, but may be made of other known plastic resins, concrete materials, or a combination of plastic resins and concrete materials.

In the backflow prevention joint 1 of the first embodiment, as shown in Figures 2 to 5, the buoyancy generating part 4 is positioned downstream of the fulcrum O about which the valve body 3 rotates. For this reason, the backflow prevention joint 1 of the first embodiment requires an operating space for the buoyancy generating part 4 to be provided downstream of the valve body 3, and is therefore suitable for attachment to the inlet 60 side of drainage equipment such as a drainage manhole 6 as shown in Figure 6, or to the drain outlet of a waterway (not shown).

In this specification, the buoyancy generating unit 4 is "located downstream of the fulcrum O" about which the valve body 3 rotates means that when the buoyancy generating unit 4 is in its raised and lowered position, the "center" that generates the buoyancy is located downstream of the vertical plane that passes through the axis of rotation of the fulcrum O about which the valve body 3 rotates. For this reason, in the first embodiment, the linking means 5 that is connected to the buoyancy generating unit 4 is also located downstream of the fulcrum O about which the valve body 3 rotates.

<Operation of the buoyancy generating portion and the valve body>
As shown in Figures 2 and 3, when the liquid level near the backflow prevention joint 1 drops under normal conditions, the buoyancy generating part 4 also drops due to its own weight in association with the drop in the liquid level. Since the second connecting means 51 is connected to the first connecting means 50 which is rotatably connected to the fulcrum P of the valve pipe 2 at the fulcrum R, the downward movement of the buoyancy generating part 4 rotates the second connecting means 51 counterclockwise around the fulcrum R in Figures 2 and 3. Therefore, the counterclockwise rotational movement of the second connecting means 51 around the fulcrum R rotates the guide arm 34 clockwise around the fulcrum O via the fulcrum Q in Figures 2 and 3. As a result, the clockwise rotational movement of the guide arm 34 rotates the valve body 3, which extends in a direction different from the direction in which the guide arm 34 extends across the fulcrum O, clockwise around the fulcrum O in Figures 2 and 3, i.e., so as to open the outlet 21 of the valve pipe 2.

As shown in Figures 4 and 5, when backflow water occurs near the backflow prevention joint 1 and the liquid level rises, the buoyancy generating part 4 also rises with the rise in the liquid level. Since the second connecting means 51 is connected to the first connecting means 50 which is rotatably connected to the fulcrum P of the valve pipe 2 at the fulcrum R, the upward movement of the buoyancy generating part 4 rotates the second connecting means 51 clockwise around the fulcrum R in Figures 4 and 5. Therefore, the clockwise rotational movement of the second connecting means 51 around the fulcrum R rotates the guide arm 34 counterclockwise around the fulcrum O via the fulcrum Q in Figures 4 and 5. As a result, the counterclockwise rotational movement of the guide arm 34 rotates the valve body 3, which extends in a direction different from the direction in which the guide arm 34 extends across the fulcrum O, counterclockwise around the fulcrum O in Figures 4 and 5, i.e., so as to close the outlet 21 of the valve pipe 2.

In this way, in the backflow prevention joint 1 of the first embodiment, in order to assist the opening and closing operation of the valve body 3, the link means 5 connected to the valve body 3 at the fulcrum Q is connected to the valve pipe 2 at the fulcrum P at a position different from the fulcrum O around which the valve body 3 rotates, so that the upward and downward movement of the buoyancy generating part 4 attached to the link means 5 can be efficiently converted into the opening and closing operation of the valve body 3. In addition, in the backflow prevention joint 1 of the first embodiment, for example, by adjusting the length of the guide arm 34 of the valve body 3 and the length of the extension arm 40 of the buoyancy generating part 4, the force generated by the upward and downward movement of the buoyancy generating part 4 can be converted to a force of the desired magnitude and easily transmitted to the valve body 3 to assist the opening and closing operation.

Therefore, in the backflow prevention joint 1 of the first embodiment, under normal circumstances, the valve body 3 is actively opened by the weight of the buoyancy generating part 4, ensuring a smooth forward flow of wastewater, and during times of flooding, the buoyancy of the buoyancy generating part 4 actively closes the valve body 3, ensuring the blocking of reverse flow of wastewater.

Second Embodiment
FIG. 7 is a perspective view showing the entire backflow prevention joint 1a according to a second embodiment of the present invention.

As shown in Fig. 7, the backflow prevention joint 1a of the second embodiment includes a valve pipe 2a having an inlet 20a and an outlet 21a, a valve body 3a rotatably attached to the valve pipe 2a to open and close the outlet 21a of the valve pipe 2a, and a buoyancy generating part 4a that rises and falls according to the height of the liquid surface. In addition, between the valve pipe 2a and the valve body 3a, a link means 5a is attached, which is composed of a first connecting arm 50a whose first end 500a is rotatably attached to the valve pipe 2a, and a second connecting arm 51a whose second end 510a is rotatably connected to the first connecting arm 50a and is rotatably attached to the valve body 3a.

In the second embodiment of the backflow prevention joint 1a, the link means 5a consisting of the first connecting arm 50a and the second connecting arm 51a functions to rotate the valve body 3a to close the outlet 21a of the valve pipe 2a as the buoyancy generating part 4a rises, and to rotate the valve body 3a to open the outlet 21a of the valve pipe 2a as the buoyancy generating part 4a descends.

Figure 8 shows a side view of the backflow prevention joint 1a shown in Figure 7 when the valve body 3a opens the valve pipe 2a, and Figure 9 shows a cross-sectional view of the backflow prevention joint 1a shown in Figure 8 taken along a cross section passing through the central axis of the valve pipe 2a. Figure 10 shows a side view of the backflow prevention joint 1a shown in Figure 7 when the valve body 3a closes the valve pipe 2a, and Figure 11 shows a cross-sectional view of the backflow prevention joint 1a shown in Figure 10 taken along a cross section passing through the central axis of the valve pipe 2a.

<Valve pipe>
In the second embodiment of the backflow prevention joint 1a, the material of the valve pipe 2a is polyvinyl chloride resin, but there is no particular limitation on the material used, and known materials such as plastics can be used. The valve pipe 2a is composed of a short straight pipe with a circular cross section except for the outlet 21a, but it does not necessarily have to be entirely straight and may include a curved pipe section. The diameter of the valve pipe 2a does not necessarily have to be uniform, and it may be configured as a differential diameter pipe joint with different diameters for the inlet 20a and the outlet 21a, for example.

In the second embodiment, the outlet 21a of the valve pipe 2a is formed so that its end face (valve seat surface) is inclined from the upstream side to the downstream side as it moves from the top to the bottom. However, in the second embodiment, when the drainage surface has not reached the buoyancy generating portion 4a, a moment acts on the valve body 3a in a direction to open the valve body 3a due to the weight of the buoyancy generating portion 4a (FIGS. 8 and 9). Therefore, the end face (valve seat surface) of the outlet 21a of the valve pipe 2a does not necessarily need to be inclined as described above, and may be a vertical surface or a surface that is inclined from the downstream side to the upstream side as it moves from the top to the bottom.

The valve body 3a is rotatably supported at the upper part of the outlet 21a of the valve pipe 2a at a fulcrum _O1 . Meanwhile, a pair of stoppers 22a are provided at the inlet 20a of the valve pipe 2a so as to extend upward from the upper end face, and a first end 500a of a first connecting arm 50a of the link means 5a is rotatably supported at the base of the stoppers 22a at a fulcrum _P1 which is a position different from the fulcrum _O1 in a side view. The stoppers 22a are convenient because when the valve pipe 2a is inserted into the outlet 61 of the catch basin 6 or the like to attach the backflow prevention joint 1a, the stoppers 22a abut against the end face of the outlet 61 to function as a stopper (see FIG. 12).

There are no particular limitations on the structures for rotatably supporting the valve body 3a and the first end 500a of the first connecting arm 50a at fulcrum _O1 and fulcrum _P1 , but in the second embodiment, fulcrum _P1 is structured so that the rotation shaft provided at the first end 500a of the first connecting arm 50a is rotatably grasped from both sides by bearings formed on each of a pair of stoppers 22a.

In addition, when the valve pipe 2a is inserted into the outlet 61 of the drainage manhole 6 to attach the backflow prevention joint 1a (Figure 12), a rubber annular valve pipe packing 23a is attached to the outer periphery of the valve pipe 2a to seal the gap between the outer periphery of the valve pipe 2a and the inner wall surface of the outlet 61, and the valve pipe packing 23a is fixed in a circumferential groove 24a formed on the outer periphery of the valve pipe 2a.

<Valve body>
In the backflow prevention joint 1a of the second embodiment, polyvinyl chloride resin is used as the material of the valve body 3a, but the material to be used is not particularly limited, and known materials such as plastics can be mainly used. In addition, the shape of the valve body 3a may be any shape that can abut against the outlet 21a of the valve pipe 2a to completely block the outlet 21a, and since the outlet 21a of the valve pipe 2a in the second embodiment has a substantially circular shape with a linear notch at the top, the valve body 3a has a substantially circular shape with a linear notch at the top when viewed from the front in accordance with the shape of the outlet 21a.

9 and 10, the second connecting arm 51a is rotatably connected to the valve disc 3a at a fulcrum _{Q1 which} is different from the fulcrum O1 about which the valve disc 3a rotates in a side view. That is, in the above configuration, the fulcrum _Q1 serves as a point of force or a point of action for opening and closing the valve disc 3a, so that the upward and downward movement generated in the buoyancy generating part 4 can be efficiently converted into the opening and closing movement of the valve disc 3a via the first connecting arm 50a and the second connecting arm 51a connected thereto.

7, the valve body 3a of the second embodiment is divided into three split valves: a central split valve body 35a attached to the outlet 21a of the valve pipe 2a at a fulcrum _O1 , and a pair of left and right split valve bodies 36a foldably connected to the left and right ends of the central split valve body 35a. Therefore, the normal valve body 3a has a shape in which the pair of left and right split valve bodies 36a are slightly bent backward with respect to the central split valve body 35a (FIGS. 7 and 8).

The valve body 3a maintains the bent shape even when it is lightly abutting against the outlet 21a of the valve pipe 2a, so that under normal circumstances, gaps are formed between the lower end of the central split valve body 35a and the outlet 21 of the valve pipe 2, and between both ends of the left and right split valve bodies 36a and the outlet 21, ensuring smooth forward flow of drainage. On the other hand, when backflow water occurs, the central split valve body 35a and the pair of left and right split valve bodies 36a are strongly pulled toward the outlet 21a of the valve pipe 2a through the link means 5a by the upward movement of the buoyancy generating part 4a described later, and deform into a flat shape that matches the end face shape of the outlet 21a (Figures 10 and 11), so that the valve body 3a completely blocks the outlet 21a of the valve pipe 2a, effectively preventing drainage from backflowing.

There are no particular limitations on the means for imparting buoyancy to the valve body 3a, but examples of configurations for imparting buoyancy include a method in which an airtight space is provided between the upstream and downstream surfaces of the valve body, making the valve body a hollow structure, and a method in which a second buoyancy generator with a specific gravity smaller than that of water is provided on the downstream surface 31 of the valve body 3.

<Linking Method>
In the backflow prevention joint 1a of the second embodiment, the link means 5a is composed of a first connecting arm 50a having a first end 500a rotatably attached to the base of the stopper 22a of the valve pipe 2a at a fulcrum _P1 , and a second connecting arm 51a rotatably connected to the first connecting arm 50a at a fulcrum _R1 and having a second end 510a rotatably attached to the valve body 3a at a fulcrum _Q1 . That is, the link means 5a has one end rotatably attached to the inlet 20a of the valve pipe 2 at the fulcrum _P1 , and the other end rotatably attached to the valve body 3a at the fulcrum _Q1 .

The first connecting arm 50a and the second connecting arm 51a are not particularly limited in shape or configuration as long as they do not interfere with each other's operations. In the second embodiment, the first connecting arm 50a is formed integrally with an extension arm 40a of the buoyancy generating unit 4a, which will be described later, and the second connecting arm 51a has a rod-like shape with shaft holes (rotation axes) formed at both ends (fulcrums _Q1 , _R1 ).

In the second embodiment, polyvinyl chloride resin is used as the material for the first connecting arm 50a and the second connecting arm 51a, but there are no particular limitations on the material used, and known materials such as plastics can be used. In addition, in this specification, the "one end", "other end" and "end" of the link means 5a do not mean the end faces of the ends of the first and second connecting arms 50a and 51a in the strict sense, but rather mean the "one end", "other end" and "end" of the link means 5a where a rotating shaft or bearing can be provided.

<Buoyancy generating part>
In the backflow prevention joint 1a of the second embodiment, the buoyancy generating part 4a, which assists and ensures the opening and closing action of the valve body 3a so that the valve body 3a does not malfunction under normal or abnormal conditions, is attached non-rotatably to the first connecting arm 50a of the link means 5a. Also, in the second embodiment, the buoyancy generating part 4a is attached to the first connecting arm 50a via a thick block-shaped extension arm 40a in order to increase the force generated by the rising and falling of the buoyancy generating part 4a and transmit it to the valve body 3a via the first connecting arm 50a and the second connecting arm 51a.

The buoyancy generating unit 4a may have a specific gravity smaller than that of water so as to generate buoyancy against backflow water, and there are no particular limitations on its shape, structure, material, etc. In the second embodiment, the buoyancy generating unit 4a is made of a hollow cylinder made of polyvinyl chloride resin, since it has a small resistance against backflow water and is easy to operate manually. In addition, the weights of the buoyancy generating unit 4a and the extension arm 40a are set so that the moment acting in the direction of opening the valve body 3a due to the weight of the buoyancy generating unit 4a is larger than the moment acting in the direction of closing the valve body 3a due to the weight of the valve body 3a at the _{fulcrum O1} of the valve tube 2a supporting the valve body 3a, in order to reliably keep the outlet 21a of the valve tube 2a open under normal conditions.

Figure 12 shows a cross-sectional view of the drainage manhole 6, showing how the backflow prevention joint 1a shown in Figure 7 is attached to the manhole 6.

The drainage manhole 6 shown in FIG. 12 is a partially enlarged lower portion of a general drainage manhole 6, as in the first embodiment, and includes an inlet 60, an outlet 61, and an inverted portion 62 connecting the inlet 60 and the outlet 61, and an opening 63 is provided above the inverted portion 62 for connecting a riser pipe (not shown) having an inspection hatch. In the second embodiment, the drainage manhole 6 is entirely molded from polyvinyl chloride resin, but may be made of other known plastic resins, concrete materials, or a combination of plastic resins and concrete materials.

In the backflow prevention joint 1a of the second embodiment, the buoyancy generating part 4a is disposed upstream of the inlet 20a of the valve pipe _2a and the fulcrum O1 about which the valve body 3a rotates, as shown in Figures 8 to 11. For this reason, the backflow prevention joint 1a of the second embodiment requires an operating space for the buoyancy generating part 4a to be provided upstream of the valve body 3a or upstream of the inlet 20a of the valve pipe 2a, and is therefore suitable for attachment to the outlet 61 side of drainage equipment such as a catch basin 6 as shown in Figure 12.

In this specification, the phrase "the buoyancy generating part 4a is disposed upstream of the fulcrum O1 about which the valve disc _3a rotates or upstream of the inlet 20a of the valve pipe 2a" means that the "center" that generates buoyancy of the buoyancy generating part 4a when it is raised or lowered is disposed upstream of a vertical plane passing through the rotation axis of the fulcrum _O1 about which the valve disc 3a rotates or upstream of the opening plane of the inlet 20a of the valve pipe 2a. For this reason, in the second embodiment, the link means 5a connected to the buoyancy generating part 4a is also disposed at least upstream of the fulcrum _O1 about which the valve disc 3a rotates.

<Operation of the buoyancy generating portion and the valve body>
As shown in Figures 8 and 9, when the liquid level near the backflow prevention joint 1a drops under normal conditions, the buoyancy generating part 4a also drops due to its own weight in association with the drop in the liquid level. Since the first connecting means 50a is connected to the valve pipe 2a at the fulcrum _P1 , the downward movement of the buoyancy generating part 4a rotates the first connecting means 50a clockwise around the fulcrum _P1 in Figures 8 and 9. Therefore, the clockwise rotational movement of the first connecting means 50a around the fulcrum _P1 moves the second connecting arm 51a from the upstream side to the downstream side via the fulcrum _R1 , and as a result, the above-mentioned movement of the second connecting arm 51a rotates the valve body 3a clockwise around the fulcrum _O1 in Figures 8 and 9 via the fulcrum _Q1 , i.e., so as to open the outlet 21a of the valve pipe 2a.

As shown in Figures 10 and 11, when backflow water occurs near the backflow prevention joint 1a and the liquid level rises, the buoyancy generating part 4a also rises with the rise in the liquid level. Since the first connecting means 50a is connected to the valve pipe _2a at the fulcrum P1, the downward movement of the buoyancy generating part 4a rotates the first connecting means 50a counterclockwise around the fulcrum _P1 in Figures 8 and 9. Therefore, the counterclockwise rotation of the first connecting means 50a around the fulcrum _P1 moves the second connecting arm 51a from the downstream side to the upstream side via the fulcrum _R1 , and as a result, the above-mentioned movement of the second connecting arm 51a rotates the valve body 3a counterclockwise around the fulcrum _O1 in Figures 8 and ₉ via the fulcrum Q1, i.e., so as to close the outlet 21a of the valve pipe 2a.

In this way, in the backflow check joint 1a of the second embodiment, in order to assist the opening and closing operation of the valve body 3a, the link means 5a connected to the valve body 3a at the fulcrum _Q1 is connected to the valve pipe 2a at the fulcrum _P1 , which is different from the fulcrum _O1 on which the valve body 3a rotates, so that the upward and downward movement of the buoyancy generating part 4a attached to the link means 5a can be efficiently converted into the opening and closing operation of the valve body 3a. Also, in the backflow check joint 1a of the second embodiment, by adjusting, for example, the distance between the fulcrum _O1 and the fulcrum _Q1 of the valve body 3a and the length of the extension arm 40a of the buoyancy generating part 4a, the force generated by the upward and downward movement of the buoyancy generating part 4a can be converted into a force of a desired magnitude and easily transmitted to the valve body 3a to assist the opening and closing operation.

Therefore, in the second embodiment of the backflow prevention joint 1a, under normal circumstances, the valve body 3a is actively opened by the weight of the buoyancy generating part 4a, ensuring a smooth forward flow of wastewater, and when the water level rises, the buoyancy of the buoyancy generating part 4a actively closes the valve body 3a, ensuring that the reverse flow of wastewater is blocked.

As described above, in the backflow prevention joints 1, 1a of the first and second embodiments, the buoyancy generating portion 4, 4a, which is provided separately from the valve body 3, 3a of the check valve, rises and falls according to the height of the liquid level of the backflowing wastewater. Link means 5, 5a are connected between the valve pipe 2, 2a and the valve body 3, 3a, which rotate the valve body 3, 3a to close the outlet 21, 21a of the valve pipe 2, 2a as the buoyancy generating portion 4, 4a rises, and rotate the valve body 3, 3a to open the outlet 21, 21a of the valve pipe 2, 2a as the buoyancy generating portion 4, 4a descends.

Therefore, even in a situation where a large amount of rainwater flows back at once and flows around the opening side (upstream side) of the valve bodies 3, 3a, the buoyancy generating parts 4, 4a raised by the backflow water reliably operate the valve bodies 3, 3a in the closing direction via the link means 5, 5a, so that the backflow water can be reliably prevented from flowing back further upstream. Also, under normal circumstances, a moment acts in the direction opening the valve bodies 3, 3a due to the weight of the buoyancy generating parts 4, 4a at the fulcrums O, _O1 of the valve pipes 2, 2a supporting the valve bodies 3, 3a, so that the smooth forward flow of drainage can be guaranteed without being impeded by the valve bodies 3, 3a.

DESCRIPTION OF SYMBOLS 1, 1a....Backflow prevention joint 2, 2a...Valve pipe 20, 20a...Inlet 21, 21a...Outlet 22...Support arm 22a...Stopper 23, 23a...Valve pipe packing 24, 24a...Circumferential groove 3, 3a...Valve body 30...Upstream surface 31...Downstream surface 32...Valve body packing 33...Fitting groove 34...Guide arm 35a...Central split valve body 36a...Left and right split valve bodies 4, 4a...Buoyancy generating section 40, 40a...Extension arm 5, 5a...Link means 50, 50a...First connecting arm 500, 500a...First end 51, 51a...Second connecting arm 510, 510a: Second end portion 511, 512: Sub-arm 6: Drainage manhole 60: Inlet 61: Outlet 62: Invert portion 63: Opening portion O, _O1 , P, _P1 , Q, _Q1 , R, _R1 : Support

Claims (10)

a valve pipe having an inlet and an outlet;
a valve body rotatably attached to the valve pipe so as to open and close the outlet of the valve pipe;
A backflow prevention joint comprising: a link means having one end rotatably attached to the valve pipe and the other end rotatably attached to the valve body; and a buoyancy generating part attached to the link means and which rises and falls according to the height of the liquid surface,
The linking means is
a first connecting arm having the one end;
a second connecting arm pivotably connected to the first connecting arm and having the other end;
The valve body is
a guide arm extending in a direction different from the direction in which the valve body extends, with a fulcrum about which the valve body rotates being sandwiched between the guide arm and the second connecting arm being rotatably connected to the guide arm;
The buoyancy generating portion is
an extension arm, and the buoyancy generating portion is attached to the second connecting arm only via the extension arm; and
A backflow prevention joint characterized in that the link means rotates the valve body to close the outlet of the valve pipe as the buoyancy generating part rises, and rotates the valve body to open the outlet of the valve pipe as the buoyancy generating part descends. The backflow prevention joint according to claim 1, characterized in that the one end of the link means is rotatably attached to the valve pipe at a fulcrum that is different from the fulcrum about which the valve body rotates. 3. The backflow prevention joint according to claim 1 , wherein the buoyancy generating portion is disposed downstream of a fulcrum about which the valve body rotates. 3. The backflow prevention joint according to claim 1 , wherein the second connecting arm is rotatably connected to the valve body at a fulcrum located at a position different from the fulcrum about which the valve body rotates. 5. The backflow prevention joint of claim 4 , wherein the buoyancy generating portion has an extension arm, and the buoyancy generating portion is attached to the first connecting arm via the extension arm. 6. The backflow prevention joint according to claim 5 , wherein the buoyancy generating portion is disposed upstream of a fulcrum about which the valve body rotates. 7. The backflow prevention joint according to claim 1, wherein the buoyancy generating portion has a specific gravity smaller than that of water. A backflow prevention joint as described in any one of claims 1 to 7 , characterized in that at the fulcrum of the valve pipe supporting the valve body, the moment generated by the weight of the buoyancy generating part is greater than the moment generated by the weight of the valve body. 9. The backflow prevention joint according to claim 1, wherein the outlet of the valve pipe is inclined from the downstream side to the upstream side as the end face of the outlet goes from the upper part to the lower part. A drainage system having an inlet or an outlet, and comprising a backflow prevention coupling according to any one of claims 1 to 9 at said inlet or said outlet.

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