JP2025017813A - Backflow prevention joint and backflow prevention system equipped with said joint - Google Patents

Abstract

To provide a backflow prevention means that allows normal flow drainage to flow smoothly under normal conditions and can reliably prevent the flow of backflow water when a backflow occurs.
[Means for solving the problem] A backflow prevention joint is provided which comprises a valve pipe having an inlet opening and an outlet opening, a valve body having a buoyancy generating portion and a valve body side hinge portion rotatably supported by a first hinge support portion provided near the outlet opening of the valve pipe, and a floater having a floater side hinge portion rotatably supported by a second hinge support portion provided near the outlet opening of the valve pipe, wherein one or more valve body side engaging teeth are provided on the outer periphery of the valve body side hinge portion and one or more floater side engaging teeth are provided on the outer periphery of the floater side hinge portion, and when a downward force is generated on the floater, the downward force causes the floater side engaging teeth to press the valve body side engaging teeth in the direction in which the valve body opens the outlet opening.
[Selected Figure] Figure 1

Description

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 characterized in that the downward force generated in the floater by its own weight keeps the valve body in an open position, and a backflow prevention system equipped with the joint in a bottomed catch basin.

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, 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. On the other hand, under normal circumstances, even if the forward flow drainage is small, there is also the issue of having to smoothly flow downstream without clogging the wastewater with foreign objects such as filth contained in the wastewater.

Therefore, 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, and to prevent clogging due to foreign matter contained in the wastewater even when the forward flow wastewater is small, a backflow prevention device has been developed in which the outlet opening against which the valve body abuts is tilted so that it retreats from top to bottom, usually forming a gap between the valve body and the outlet opening to ensure a flow path, as described in, for example, JP 2020-153508 A (Patent Document 1).

In addition, in the backflow prevention device described in Patent Document 1, the valve body is usually always open, so when a backflow occurs, it may be unstable as to whether the valve body reliably closes the outlet opening. Therefore, even in backflow prevention devices in which the outlet opening is tilted backward like in Patent Document 1, backflow prevention devices have been developed in which a float is attached to the lid (valve body), as described in, for example, JP 10-18405 A (Patent Document 2), to make the closing action of the valve body more reliable when a backflow occurs.

JP 2020-153508 A Japanese Patent Application Publication No. 10-18405

However, in the backflow prevention devices described in Patent Documents 1 and 2, the outlet opening is inclined so that it is receded, and the valve body, which is normally suspended by its own weight, is kept in an open state with the outlet opening. This means that when backflow occurs, the backflowing water flows around to the upstream back surface of the valve body (the gap between the valve body and the outlet opening) before it reaches the downstream surface of the valve body, making it difficult for the valve body to close the outlet opening, and there are cases where the backflow of wastewater cannot be prevented.

The present invention aims to provide a backflow prevention means that allows for smooth drainage even when the amount of forward flow drainage is small under normal circumstances, and can also reliably prevent backflow water from flowing when backflow occurs.

After extensive research into the structure of the backflow prevention means and the flow of wastewater, the inventors discovered that by inclining the outlet opening of the backflow prevention means so that it advances from upstream to downstream as it moves vertically or from top to bottom, the blocking ability of the valve body when a backflow occurs can be improved, and that for forward flow wastewater, a smooth flow can be ensured by linking the opening of the valve body under normal conditions with the movement of the floater descending under its own weight, which led to the completion of this invention.

That is, according to the present invention, a backflow prevention joint is provided that includes a valve pipe having an inlet opening and an outlet opening, a valve body having a valve body side hinge part that has a buoyancy generating part and is rotatably supported by a first hinge support part provided near the outlet opening of the valve pipe, and a floater having a floater side hinge part that is rotatably supported by a second hinge support part provided near the outlet opening of the valve pipe, in which one or more valve body side engagement teeth are provided on the outer periphery of the valve body side hinge part, and one or more floater side engagement teeth are provided on the outer periphery of the floater side hinge part, and when a downward force is generated on the floater, the downward force causes the floater side engagement teeth to press the valve body side engagement teeth in the direction in which the valve body opens the outlet opening, in other words, the floater side engagement teeth engage with the valve body side engagement teeth to rotate the valve body in the direction in which the outlet opening is opened.

According to the present invention, the outlet opening of the valve pipe is inclined so as to advance from the upstream side to the downstream side as it moves vertically or from top to bottom, so that the occlusion property of the valve body when backflow occurs is enhanced, and the flow of backflow water can be reliably suppressed. In addition, one or more engagement teeth are provided on the outer periphery of the hinge part on the valve body side and the outer periphery of the hinge part on the floater side, and when a downward force is generated on the floater due to its own weight, the downward force causes the floater side engagement tooth to press the valve body side engagement tooth in the direction in which the valve body opens the outlet opening, so that under normal circumstances, the valve body keeps the outlet opening open, ensuring a smooth flow of forward flow drainage even when the forward flow drainage is small, and preventing clogging due to foreign matter contained in the drainage.

In the backflow prevention joint of the present invention, the range of rotation of the valve body in the opening direction may be restricted by the valve body abutting against the floater, or a stopper may be provided on the first hinge support part of the valve tube, and the range of rotation of the valve body in the opening direction may be restricted by the valve body side engagement teeth engaging with the stopper.

In a backflow prevention joint, if the rotation range of the valve body toward 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 close the outlet opening. Therefore, in the present invention, a floater or a dedicated stopper 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 rotate reliably to close the outlet opening without malfunctioning due to backflow water.

The backflow prevention joint of the present invention may be configured so that when an upward force is generated in the floater, the floater side engagement teeth do not press the valve body side engagement teeth in the direction in which the valve body closes the outlet opening, in other words, the floater side engagement teeth and the valve body side engagement teeth are disengaged.

In other words, the backflow prevention joint of the present invention is a backflow prevention joint comprising a valve pipe having an inlet opening and an outlet opening, a valve body rotatably supported near the outlet opening of the valve pipe, a floater having a buoyancy generating portion rotatably supported near the outlet opening of the valve pipe, and a connecting means for linking or unlinking the operation of the valve body and the operation of the floater, and the valve body and the floater can be configured so that the valve body and the floater are connected by the connecting means so that the downward movement of the floater rotates the valve body in the opening direction, and are unconnected so that the upward movement of the floater does not rotate the valve body in the closing direction.

When the above-mentioned configuration is adopted in the present invention, when a downward force is generated on the floater due to its own weight, the valve body receives a force from the floater via the floater side engagement teeth and the valve body side engagement teeth to rotate in a direction to open the outlet opening, but when an upward force is generated on the floater due to buoyancy, the floater side engagement teeth and the valve body side engagement teeth are disengaged, and the valve body is essentially free to not receive any force from the floater. Therefore, the valve body will rotate naturally and smoothly in a direction to close the outlet opening as the downstream surface receives pressure from the backflowing water.

The backflow prevention joint of the present invention can be configured so that when an upward force is generated on the floater, the floater side engagement teeth press the valve body side engagement teeth in the direction in which the valve body closes the outlet opening due to the upward force, in other words, the floater side engagement teeth engage with the valve body side engagement teeth, causing the valve body to rotate in the direction in which the outlet opening is closed. In other words, the opening and closing action of the valve body can be configured to be linked to the movement of the floater, whether the floater descends due to its own weight or rises due to buoyancy.

In this case, the valve will not be fully closed unless the backflow water level reaches a specified set level, but once the backflow water level reaches or exceeds the set level, the valve will reliably close the outlet opening without malfunctioning and will be able to maintain that state.

The backflow prevention joint of the present invention may also be attached as a backflow prevention system to the inlet of a bottomed catch basin that has an inlet that opens horizontally, an outlet that communicates with the inlet and also opens horizontally, and an inspection hatch that communicates with the inlet and the outlet and also opens upward. Note that in this specification, "upward" means "upward" facing approximately vertically, and does not mean "vertically upward" facing vertically in the strict sense.

According to the backflow prevention joint of the present invention, the outlet opening of the valve pipe is inclined so as to advance from the upstream side to the downstream side as it moves vertically or from top to bottom, so that the blocking ability of the valve body when backflow occurs is enhanced, and the flow of backflow water can be reliably prevented. In addition, one or more engagement teeth are provided on the outer periphery of the hinge part on the valve body side and the outer periphery of the hinge part on the floater side, and when a downward force is generated on the floater due to its own weight, the downward force causes the floater side engagement tooth to press the valve body side engagement tooth in the direction in which the valve body opens the outlet opening, so that under normal circumstances, the valve body keeps the outlet opening open, ensuring a smooth flow of forward flow drainage even when the forward flow drainage is small, and preventing clogging due to foreign matter contained in the drainage.

With the backflow prevention joint of the present invention, when an upward force is generated in the floater, the floater side engagement teeth disengage from the valve body side engagement teeth so that the upward force does not press the valve body in the direction of closing the outlet opening, and the valve body will rotate naturally and smoothly in the direction of closing the outlet opening as the downstream surface receives pressure from the backflow water.

In addition, according to the backflow prevention joint of the present invention, when an upward force is generated in the floater, the floater side engagement teeth press the valve body side engagement teeth in the direction in which the valve body closes the outlet opening due to the upward force, in other words, the floater side engagement teeth engage with the valve body side engagement teeth to rotate the valve body in the direction in which the outlet opening is closed. In this case, when the liquid level of the backflow water reaches a set level or higher, the valve body can reliably close the outlet opening without malfunctioning and maintain that state.

1 is a perspective view showing an overall outline of a backflow prevention joint according to one embodiment of the present invention; 2 is a cross-sectional view of the backflow prevention joint shown in FIG. 1 taken along line AA. 2 is a perspective view showing a valve body of the backflow prevention joint shown in FIG. 1. 2 is a perspective view showing a floater of the backflow prevention joint shown in FIG. 1. FIG. 2 is a perspective view showing a valve pipe of the check joint shown in FIG. 1. FIG. 2 is a partial cross-sectional view showing a schematic diagram of the movement of the valve body and the floater of the backflow prevention joint shown in FIG. 1. 1 is a perspective view showing an overall overview of a backflow prevention system (partially transparent) according to one embodiment of the present invention. FIG. 8 is a cross-sectional view of the backflow prevention system shown in FIG. 7 taken along line BB. FIG. 11 is a perspective view showing an overall outline of a backflow prevention joint according to another embodiment of the present invention. 10 is a cross-sectional view of the backflow prevention joint shown in FIG. 9 taken along the line CC. 10 is a perspective view showing a valve body of the backflow prevention joint shown in FIG. 9 . 10 is a perspective view showing a floater of the backflow prevention joint shown in FIG. 9 . 10 is a perspective view showing a valve pipe of the check joint shown in FIG. 9 . FIG. 10 is a partial cross-sectional view showing a schematic diagram of the movement of the valve body and the floater of the backflow prevention joint shown in FIG. 9 . FIG. 2 is a perspective view showing an overall outline of a backflow prevention system (partially transparent) according to another embodiment of the present invention. FIG. 16 is a cross-sectional view of the backflow prevention system shown in FIG. 15 taken along line DD.

The backflow prevention joint 1, 1a according to one embodiment of the present invention and the backflow prevention system 2, 2a to which the joint 1, 1a is attached will be described in detail below 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.

1. First embodiment <Backflow prevention joint>
Fig. 1 shows a perspective view illustrating the overall outline of a backflow prevention joint 1 according to a first embodiment of the present invention, and Fig. 2 shows a cross-sectional view taken along line A-A of the backflow prevention joint 1 shown in Fig. 1. Of the backflow prevention joint 1 shown in Fig. 1, Fig. 3 shows a perspective view illustrating a valve body 3, Fig. 4 shows a perspective view illustrating a floater 4, and Fig. 5 shows a perspective view illustrating a valve pipe 5.

As shown in Figures 1 and 2, the backflow prevention joint 1 of the first embodiment includes a cylindrical valve pipe 5 (Figure 5) having an inlet opening 50 and an outlet opening 51, a valve body 3 (Figure 3) rotatably supported near the outlet opening 51 of the valve pipe 5, and a floater 4 (Figure 4) having a buoyancy generating part 40 and rotatably supported on the valve pipe 5 in the same manner as the valve body 3. In the first embodiment, the floater 4 is configured separately and independently from the valve body 3 so that gravity generated in the floater 4 and buoyancy generated in the buoyancy generating part 40 work efficiently, and the buoyancy generating part 40 of the floater 4 is arranged so that it can rotate away from the valve body 3 in the area downstream of the valve body 3 and/or in the area above the valve body 3.

In addition, in the first embodiment, the backflow prevention joint 1 is made of polyvinyl chloride resin, but there are no particular limitations on the material used, and known materials such as plastic can be used.

<Valve body>
The backflow prevention joint 1 of the first embodiment includes a valve body 3 for opening and closing a valve seat 52 formed in an outlet opening 51 of a valve pipe 5 described later. The valve body 3 is not particularly limited in shape as long as it can abut against and close the valve seat 52, and in the first embodiment, the downstream surface 33 of the valve body 3 has a shape that is concave from the downstream side to the upstream side (the upstream back surface 34 has a shape that bulges from the downstream side to the upstream side) (FIG. 2).

In this case, the valve body 3 does not receive a large force even when the wastewater collides with the upstream back surface 34 that bulges upstream, but receives a large force when the wastewater collides with the downstream surface 33 that is recessed upstream. Therefore, when backflow occurs, the backflow water mainly collides with the downstream surface 33 of the valve body 3, so the valve body 3 receives a large force and operates to close the outlet opening 51, and can reliably prevent the backflow of wastewater. In addition, in the first embodiment, a groove is provided on the peripheral portion of the valve body 3 at a position where it abuts against the valve seat portion 52, and a packing 30 made of an elastic material such as rubber is fitted into the groove to improve the sealing with the outlet opening 51.

A valve body side hinge portion 31 extending in the radial direction is formed on the upper peripheral edge of the valve body 3, and one valve body side engagement tooth 32 protruding in the radial direction from the outer peripheral surface is formed on the outer periphery of the rotation axis O of the valve body side hinge portion 31. There is no particular limit to the shape or number of the valve body side engagement tooth 32, but in the first embodiment, the valve body side engagement tooth 32 is a convex portion having a smooth triangular cross section, and may be formed from a convex portion and/or a concave portion to form one tooth of a gear. In addition, the valve body side engagement tooth 32 may be one or two or more, as long as the number is such that it can engage with the floater side engagement tooth 42 at least when the floater 4 descends.

<Floater>
The backflow prevention joint 1 of the first embodiment is equipped with a floater 4 to assist the movement of the valve body 3. The floater 4 has a buoyancy generating part 40, and is not particularly limited as long as it generates a force to rotate the valve body 3 in the opening direction by the weight of the floater 4 and has a shape, structure, and material that can generate buoyancy against the weight of the floater 4 in water. In the first embodiment, the buoyancy generating part 40 is set so that the rotational moment generated by the weight of the floater 4 at the rotation axis P of the floater 4 is larger than the rotational moment generated by the weight of the valve body 3 at the rotation axis O of the valve body 3, and the rotational moment generated by the buoyancy of the buoyancy generating part 40 at the rotation axis P of the floater 4 is set so that it is larger than the rotational moment generated by the weight of the floater 4.

As shown in FIG. 2, in the first embodiment, the buoyancy generating portion 40 of the floater 4 is formed as a hollow plastic structure having a thick disk shape because it is strong and easy to manufacture. The buoyancy generating portion 40 is composed of a disk-shaped dish portion 43 and a disk-shaped cap portion 44, and is formed so that a cavity is maintained inside by joining the peripheral portion of the dish portion 43 and the peripheral portion of the cap portion 44 liquid-tightly.

A floater side hinge portion 41 extending in the radial direction is formed on the upper peripheral portion of the plate portion 43 of the floater 4, and one floater side engagement tooth 42 protruding in the radial direction from the outer peripheral surface is formed on the outer periphery of the rotation axis P of the floater side hinge portion 41. There is no particular restriction on the shape or number of the floater side engagement tooth 42, but in the first embodiment, the floater side engagement tooth 42 is a convex portion having a smooth triangular cross section similar to the valve body side engagement tooth 32, and may be formed from a convex portion and/or a concave portion to form one tooth of a gear. In addition, the floater side engagement tooth 42 may be one or two or more, as long as the number is such that it can engage with the valve body side engagement tooth 32 at least when the floater 4 descends.

As shown in Figs. 1 and 4, in the first embodiment, the floater side hinge portion 41 has a first protrusion 410 and a second protrusion 411 protruding in a rectangular parallelepiped shape from its side surface. The first protrusion 410 abuts against the hinge support portion 51 of the valve tube 5 when the floater 4 rotates upward, thereby functioning as a stopper that restricts the rotation range of the floater 4 on the ascending side, and the second protrusion 411 abuts against the hinge support portion 51 of the valve tube 5 when the floater 4 rotates downward, thereby functioning as a stopper that restricts the rotation range of the floater 4 on the descending side. In the first embodiment, the rotation range of the floater 4 on the ascending side can also be restricted by abutting against the valve body 3, so that the use of the valve body 3 can be prioritized for restriction, the use of the first protrusion 410 can be prioritized for restriction, or both can be arranged to function simultaneously for restriction.

<Valve pipe>
5, the valve pipe 5 has a substantially circular inlet opening 50 for attachment to an inlet of a catch basin or the like or an outlet of a pipe (neither of which are shown), and a substantially circular outlet opening 51 that communicates with the inlet opening 50 and forms a valve seat 52 that abuts against the valve body 3. A groove is provided in the circumferential direction on the outer periphery of the valve pipe 5, and a packing 53 made of an elastic material such as rubber is fitted into the groove to improve the sealing performance with the inlet of a catch basin or the outlet of a pipe to which the backflow prevention joint 1 is attached.

In the first embodiment, the valve pipe 5 is 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. The diameter of the valve pipe 5 does not necessarily have to be uniform, and it may be configured, for example, as a differential diameter pipe joint in which the diameters of the inlet opening 50 and the outlet opening 51 are different.

In the first embodiment, the outlet opening 51 (valve seat 52) of the valve pipe 5 is formed vertically (Figure 2), but it may be formed at an incline so as to advance from the upstream side to the downstream side as it moves from top to bottom (not shown). If the outlet opening 51 (valve seat 52) of the valve pipe 5 is shaped as described above, when the movement of the valve body 3 is not linked to the movement of the floater 4, the valve body 3 can close the outlet opening 51 (valve seat 52) by its own weight alone, and the ability of the valve body 3 to close the outlet opening 51 is enhanced.

In addition, in the first embodiment, under normal circumstances, the movement of the valve body 3 is linked to the movement of the floater 4 which tends to descend under its own weight, and the weight of the floater 4 keeps the valve body 3 with the outlet opening 51 (valve seat portion 52) open, so even if the amount of forward flow drainage is small, a smooth flow of forward flow drainage is guaranteed, and clogging due to foreign matter contained in the drainage does not occur.

As shown in Figures 1, 2 and 5, a hinge support part 54 is provided on the upper part of the valve pipe 5 for rotatably supporting the valve body side hinge part 31 of the valve body 3 and the floater side hinge part 41 of the floater 4. There are no particular limitations on the shape or number of the hinge support parts 54, and they may be configured separately as a first hinge support part for supporting the valve body side hinge part 31 and a second hinge support part for supporting the floater side hinge part 41.

In the first embodiment, the hinge support part 54 is arranged on the side of the valve body side hinge part 31 so that the axial hole of the hinge support part 54 is aligned with the axial hole of the valve body side hinge part 31, and the valve body 3 is rotatably supported by inserting one pin O through each axial hole. The hinge support part 54 is also arranged on the side of the floater side hinge part 41 above the valve body side hinge part 31 so that the axial hole of the hinge support part 54 is aligned with the axial hole of the floater side hinge part 41, and the floater 4 is rotatably supported by inserting one pin P through each axial hole. Furthermore, a partition-shaped insertion stopper 55 is provided on the upper part of the valve pipe 5 and upstream of the hinge support part 54 to prevent excessive insertion when attaching the inlet opening 50 of the valve pipe 5 to an inlet of a drainage basin or the like or to the outlet of a piping.

As for the configuration of the valve body side hinge part 31, the floater side hinge part 41 and the hinge support part 54, a pair of hinge support parts 54 may be provided on the valve tube 5 so as to sandwich one valve body side hinge part 31 or one floater side hinge part 41 from both sides as in the first embodiment, or, although not shown, a pair of valve body side hinge parts or a pair of floater side hinge parts may be provided on the valve body or the floater so as to sandwich one hinge support part of the valve tube from both sides. In order to distribute the force acting on the pin as evenly as possible, it is preferable to provide at least two or more of either the valve body side and floater side hinge parts or the hinge support parts.

<Valve body and floater movement>
Fig. 6 shows a partial cross-sectional view that shows the movement of the valve body 3 and the floater 4 of the backflow prevention joint 1 according to the first embodiment. In Fig. 6, (a) shows the state of the valve body 3 and the floater 4 when basically no backflow water is occurring, (b) shows the state when the backflow water raises the floater 4 and the valve body 3 closes the outlet opening 51, and (c) shows the state when the backflow water increases even after the valve body 3 closes the outlet opening 51 and the rise of the floater 4 reaches its upper limit. The movement of the valve body 3 and the floater 4 will be explained below in the order of (a), (b), and (c) in Fig. 6.

<Aspect (a)>
6A shows a normal state in which no backflow water is generated in a catch basin or the like to which the backflow prevention joint 1 according to the first embodiment is attached, and only forward flow drainage flows. In this case, no buoyancy is generated in the buoyancy generating part 40, and the rotational moment generated in the floater side hinge part 41 due to the weight of the floater 4 is greater than the rotational moment generated in the valve body side hinge part 31 due to the weight of the valve body 3. Therefore, a downward force is generated in the floater 4, and the floater side engagement teeth 42 press the valve body side engagement teeth 32 in the direction in which the valve body 3 opens the outlet opening 51, so that the valve body 3 holds the outlet opening 51 of the valve pipe 5 in an open state. In other words, the downward movement of the floater 4 connects and links the floater side engagement teeth 42 with the valve body side engagement teeth 32, and rotates the valve body 3 in the opening direction.

In addition, in the embodiment shown in FIG. 6(a), when backflow water or the like occurs and the buoyancy generated in the buoyancy generating portion 40 generates an upward force on the floater 4, the upward force rotates the floater side engagement teeth 42 away from the valve body side engagement teeth 32, so the valve body side engagement teeth 32 are not pressed in the direction in which the valve body 3 closes. In other words, the upward movement of the floater 4 causes the floater side engagement teeth 42 to be in a state of being unconnected and unlinked from the valve body side engagement teeth 32, and does not rotate the valve body 3 in the direction in which it closes. However, even if the movement of the valve body 3 is in a state of being unconnected and unlinked with the movement of the floater 4, the valve body 3 itself naturally rotates in the direction in which it closes due to its own weight, so that the valve body side engagement teeth 32 may maintain a state of abutment so as to follow the floater side engagement teeth 42 until the valve body 3 appears to close the outlet opening 51 (the embodiment of FIG. 6(b) described later).

In this manner, in the embodiment shown in FIG. 6(a), one or more valve body side engagement teeth 32 are provided on the outer periphery of the valve body side hinge portion 31, and one or more floater side engagement teeth 42 are provided on the outer periphery of the floater side hinge portion 41. When a downward force is generated on the floater 4 due to its own weight, the floater side engagement teeth 42 press the valve body side engagement teeth 32 in the direction in which the valve body 3 opens the outlet opening 51, so that under normal circumstances, the valve body 3 keeps the outlet opening 51 open, ensuring a smooth flow of forward flow drainage even when the amount of forward flow drainage is small, and no clogging occurs due to foreign matter contained in the drainage.

In the backflow prevention joint 1, if the rotation range of the valve body 3 in the opening direction becomes too large, backflow water may collide with the upstream back surface 34 of the valve body 3 when a backflow occurs, and the valve body 3 may not operate in the closing direction. Therefore, in the first embodiment, when the floater 4 rises, the valve body 3, which rotates in the direction to open the outlet opening 51 in conjunction with the floater 4's movement, is configured to abut against the floater 4, thereby restricting the rotation range of the valve body 3 in the opening direction. In addition, although not shown, the rotation range of the valve body 3 in the opening direction may be restricted by providing a stopper on the hinge support part 54 that supports the valve body side hinge part 31 and engaging the valve body side engagement tooth 32 with the stopper.

In this way, in the backflow prevention fitting 1 of the first embodiment, the floater 4 or a dedicated stopper functions as a stopper that restricts the rotation range of the valve body 3, ensuring that backflow water collides with the downstream surface 33 of the valve body 3, and ensuring that the valve body 3 rotates to the closing side without malfunctioning due to backflow water.

<Aspect (b)>
6(b) shows a state in which backflow water (not shown) occurs in a catch basin or the like to which the backflow prevention joint 1 according to the first embodiment is attached, and the backflow water raises the floater 4, causing the valve body 3 to close the outlet opening 51. In this case, buoyancy is generated in the buoyancy generating part 40 by the backflow water, and the rotational moment generated in the floater side hinge part 41 by the buoyancy of the buoyancy generating part 40 is greater than the rotational moment generated in the floater side hinge part 41 by the weight of the floater 4. Therefore, a total upward force is generated in the floater 4, and at that time, the floater side engagement teeth 42 rotate so as to move away from the valve body side engagement teeth 32 due to the upward force, so that the valve body side engagement teeth 32 are not pressed in the direction in which the valve body 3 closes. In other words, the upward movement of the floater 4 causes the floater side engagement teeth 42 to be uncoupled and unlinked from the valve body side engagement teeth 32, and does not rotate the valve body 3 in the direction in which it closes. However, as shown in Figure 6 (b), even if the movement of the valve body 3 is not connected or linked to the movement of the floater 4, the valve body side engagement teeth 32 may appear to remain in contact with the floater side engagement teeth 42.

In this manner, in the embodiment shown in FIG. 6(b), one or more valve body side engagement teeth 32 are provided on the outer periphery of the valve body side hinge portion 31, and one or more floater side engagement teeth 42 are provided on the outer periphery of the floater side hinge portion 41. When an upward force is generated on the floater 4, the upward force does not cause the floater side engagement teeth 42 to press the valve body side engagement teeth 32 in the direction in which the valve body 3 closes. Therefore, the valve body 3 is in a state in which it is freely suspended and swings freely, and naturally rotates in the direction in which the outlet opening 51 is closed due to its own weight, so that the backflow water collides with the downstream side surface 33 of the valve body 3 before the upstream side back surface 34, and the valve body 3, which receives pressure from the downstream side surface 33 by the backflow water, naturally and smoothly rotates in the direction in which the outlet opening 51 is closed.

<Aspect (c)>
Figure 6(c) shows a state in which, in a catch basin or the like to which the backflow prevention joint 1 according to the first embodiment is attached, the backflow water increases even after the valve body 3 closes the outlet opening 51 (the state of Figure 6(b)), and the rise of the floater 4 reaches its upper limit. In this case, as in the state of Figure 6(b), an upward force is generated in the floater 4 due to the buoyancy of the buoyancy generating part 40, and at that time, the floater side engagement teeth 42 rotate away from the valve body side engagement teeth 32 due to the upward force, so that the valve body side engagement teeth 32 are not pressed in the direction in which the valve body 3 closes. In other words, even in the state of Figure 6(c), the upward movement of the floater 4 causes the floater side engagement teeth 42 to be uncoupled and unlinked from the valve body side engagement teeth 32, and does not rotate the valve body 3 in the closing direction. With the valve body 3 keeping the outlet opening 51 closed, the floater 4 rises independently of the valve body 3 from the position shown by the thin imaginary line to the position shown by the solid line where the floater 4 reaches the upper limit of its rotation range.

In this way, in the embodiment shown in FIG. 6(c), one or more valve body side engagement teeth 32 are provided on the outer periphery of the valve body side hinge portion 31, and one or more floater side engagement teeth 42 are provided on the outer periphery of the floater side hinge portion 41. When an upward force is generated on the floater 4, the upward force does not cause the floater side engagement teeth 42 to press the valve body side engagement teeth 32 in the direction in which the valve body 3 closes. Therefore, even in the embodiment shown in FIG. 6(c), the valve body 3 is in a state of being freely suspended so as to be swingable, and naturally rotates in the closing direction due to its own weight, so that the backflow water collides with the downstream side surface 33 of the valve body 3 before the upstream side back surface 34, and the valve body 3, which is pressured by the backflow water, naturally and smoothly rotates in the direction in which the outlet opening 51 is closed.

There are no particular limitations on the rotation range of the valve body 3 and the floater 4, but in the first embodiment, in order to ensure smooth forward flow drainage and high degree of occlusion of the valve body 3 when backflow occurs, the rotation range of the valve body 3 is set to 60 to 80° from the outlet opening 51 (valve seat 52), and the rotation range of the floater 4 is set to 95 to 145° from the outlet opening 51 (valve seat 52).

<Backflow prevention system>
Figure 7 shows an oblique view illustrating an overall overview of the backflow prevention system 2 (partially transparent) according to the first embodiment of the present invention, and Figure 8 shows a cross-sectional view B-B of the backflow prevention system 2 shown in Figure 7.

As shown in Figures 7 and 8, the backflow prevention system 2 of the first embodiment is constructed by attaching the above-mentioned backflow prevention joint 1 of the present invention to the inlet 61 of a bottomed drainage basin 6.

More specifically, the drainage manhole 6 used in the backflow prevention system 2 of the first embodiment has a bottom 60, an inlet 61 that opens horizontally, an outlet 62 that communicates with the inlet 61 and opens horizontally, and an inspection port 63 that communicates with the inlet 61 and the outlet 62 and opens upward. In this embodiment, the inlet 61, the outlet 62, and the inspection port 63 all have a receiving port shape, and an upstream connecting pipe 71, a downstream connecting pipe 72, and a riser pipe 70 are connected to the inside of each receiving port 61, 62, and 63.

In the first embodiment of the backflow prevention system 2, the drain manhole 6, the upstream connecting pipe 71, the downstream connecting pipe 72, and the riser pipe 70 are made of polyvinyl chloride resin, but there are no particular limitations on the materials used, and known materials such as plastics can be used.

In the first embodiment of the backflow prevention system 2, the backflow prevention joint 1 of the present invention is attached by inserting the inlet opening 50 of the backflow prevention joint 1 from inside the drainage manhole 6 into the inlet 61, and a gasket 53 is provided on the outer periphery of the valve pipe 5, so that the outer periphery of the valve pipe 5 and the inner periphery of the inlet 61 are liquid-tightly sealed, and the backflow prevention joint 1 does not easily fall out of the inlet 61.

In the first embodiment of the backflow prevention system 2, the drain manhole 6 has an inspection port 63 that opens upward above the inlet 61 and outlet 62, so that the valve body 3 and floater 4 do not interfere with the inner walls of the drain manhole 6 or the riser pipe 70, and their movement is not hindered. In addition, a partition-shaped insertion stop 55 is provided on the upper part of the valve pipe 5, upstream of the hinge support part 54, so that the backflow prevention joint 1 only needs to be pushed in until the insertion stop 55 abuts against the inner wall of the drain manhole 6 or the riser pipe 70, and excessive insertion is prevented from interfering with the inner wall of the drain manhole 6, and thus preventing their movement from being hindered.

According to the first embodiment of the backflow prevention system 2, the backflow prevention fitting 1 attached to the inlet 61 of the drainage manhole 6 tilts the outlet opening 51 of the valve pipe 5 vertically or from top to bottom, progressing from the upstream side to the downstream side, thereby increasing the blocking ability of the valve body 3 when backflow occurs and reliably preventing the flow of backflow water.

In addition, according to the first embodiment of the backflow prevention system 2, one or more engagement teeth 32, 42 are provided on the outer periphery of the hinge part 31 on the valve body side and the outer periphery of the hinge part 41 on the floater side. When a downward force is generated on the floater 4 due to its own weight, the downward force causes the floater side engagement tooth 42 to press the valve body side engagement tooth 32 in the direction in which the valve body 3 opens the outlet opening 51. Therefore, under normal circumstances, the valve body 3 keeps the outlet opening 51 open, ensuring a smooth flow of forward flow drainage even when the amount of forward flow drainage is small, and no clogging occurs due to foreign matter contained in the drainage.

2. Second embodiment <Backflow prevention joint>
Fig. 9 shows a perspective view illustrating the overall outline of a backflow prevention joint 1a according to a second embodiment of the present invention, and Fig. 10 shows a CC cross-sectional view of the backflow prevention joint 1a shown in Fig. 9. Of the backflow prevention joint 1a shown in Fig. 9, Fig. 11 shows a perspective view illustrating the valve body 3a, Fig. 12 shows a perspective view illustrating the floater 4a, and Fig. 13 shows a perspective view illustrating the valve pipe 5a.

As shown in Figures 9 and 10, the backflow prevention joint 1 of the second embodiment includes a cylindrical valve pipe 5a (Figure 13) having an inlet opening 50a and an outlet opening 51a, a valve body 3a (Figure 11) rotatably supported near the outlet opening 51a of the valve pipe 5a, and a floater 4a (Figure 12) having a buoyancy generating portion 40a and rotatably supported on the valve pipe 5a in the same manner as the valve body 3a. In the second embodiment, the floater 4a is configured separately and independently from the valve body 3a so that the gravity generated in the floater 4a and the buoyancy generated in the buoyancy generating portion 40a work efficiently, and the buoyancy generating portion 40a of the floater 4a is arranged so that it can rotate away from the valve body 3a in the area downstream of the valve body 3a and/or the area above the valve body 3a.

In the second embodiment, the backflow prevention joint 1a is made of polyvinyl chloride resin, but there is no particular limitation on the material used, and known materials such as plastic can be used.

<Valve body>
The backflow prevention joint 1a of the second embodiment includes a valve body 3a for opening and closing a valve seat 52a formed in an outlet opening 51a of a valve pipe 5a described later. The shape of the valve body 3a is not particularly limited as long as it can abut against and close the valve seat 52a, and in the second embodiment, the downstream surface 33a of the valve body 3a has a shape that is recessed from the downstream side to the upstream side (the upstream back surface 34a has a shape that bulges from the downstream side to the upstream side) (FIG. 10).

In this case, the valve body 3a does not receive a large force even when the wastewater collides with the upstream back surface 34a that bulges upstream, but receives a large force when the wastewater collides with the downstream surface 33a that is recessed upstream. Therefore, when backflow occurs, the backflow water mainly collides with the downstream surface 33a of the valve body 3a, so the valve body 3a receives a large force and operates to close the outlet opening 51a, and can reliably prevent the backflow of wastewater. In the second embodiment, a groove portion 35a is provided on the peripheral portion of the valve body 3a at a position where it abuts against the valve seat portion 52a, and a packing (not shown) made of an elastic material such as rubber can be fitted into the groove portion 35a to improve the sealing performance with the outlet opening 51a.

A radially extending valve body side hinge portion 31a is formed on the upper peripheral edge of the valve body 3a, and a gear-shaped valve body side engagement tooth 32a consisting of two or more teeth protruding in the radial direction from the outer peripheral surface is formed on the outer periphery of the rotation axis O of the valve body side hinge portion 31a. The shape and number of the valve body side engagement tooth 32a are not particularly limited, but in the second embodiment, one tooth of the valve body side engagement tooth 32a is a convex portion having a smooth triangular cross section, and may be formed from a convex portion and/or a concave portion as long as it forms the teeth of a gear. In addition, the valve body side engagement tooth 32a may be one or two or more as long as it can engage with the floater side engagement tooth 42a when the floater 4a rises and falls. For example, one floater side engagement tooth 42a is formed on the outer circumferential surface of the floater side hinge part 41a, and two or more valve body side engagement teeth 32a are formed on the outer circumferential surface of the valve body side hinge part 31a so as to sandwich the floater side engagement tooth 42a from the front and rear.

<Floater>
The backflow prevention joint 1a of the second embodiment is equipped with a floater 4a to assist the movement of the valve body 3a. The floater 4a has a buoyancy generating part 40a, and is not particularly limited as long as it generates a force to rotate the valve body 3a in the opening direction by the weight of the floater 4a and has a shape, structure, and material that can generate buoyancy against the weight of the floater 4a in water. In the second embodiment, the buoyancy generating part 40a is set so that the rotational moment generated by the weight of the floater 4a at the rotation axis P of the floater 4a is larger than the rotational moment generated by the weight of the valve body 3a at the rotation axis O of the valve body 3a, and the rotational moment generated by the buoyancy of the buoyancy generating part 40a at the rotation axis P of the floater 4a is set so that it is larger than the rotational moment generated by the weight of the floater 4a.

As shown in Figure 10, in the second embodiment, the buoyancy generating part 40a of the floater 4a is formed as a hollow plastic structure and has a spherical shape because it is strong and easy to manufacture. The buoyancy generating part 40a is connected to the floater side hinge part 41a via a round bar-shaped rod 45a, and by adjusting the size of the buoyancy generating part 40a and the length of the rod 45a, the magnitude of the rotational moment generated on the rotation axis P by the buoyancy of the buoyancy generating part 40a can be adjusted.

On the outer periphery of the rotation axis P of the floater side hinge part 41a, gear-shaped floater side engagement teeth 42a consisting of two or more teeth protruding radially from the outer periphery are formed. There is no particular restriction on the shape or number of the floater side engagement teeth 42a, but in the second embodiment, one tooth of the floater side engagement teeth 42a is a convex part having a smooth triangular cross section like the valve body side engagement teeth 32a, and may be formed from a convex part and/or a concave part as long as it forms gear teeth. In addition, the floater side engagement teeth 42a may be one or two or more as long as they can engage with the valve body side engagement teeth 32a when the floater 4a rises and falls. For example, there is a case where one valve body side engagement tooth 32a is formed on the outer periphery of the valve body side hinge part 31a, and two or more floater side engagement teeth 42a are formed on the outer periphery of the floater side hinge part 41a so as to sandwich the valve body side engagement teeth 32a from the front and rear.

9 and 12, in the second embodiment, the floater side engagement teeth 42a are divided into the first row of floater side engagement teeth 420a and the second row of floater side engagement teeth 421a, and the first row of floater side engagement teeth 420a and the second row of floater side engagement teeth 421a are arranged in a staggered manner. By dividing the floater side engagement teeth 42a into the first row of floater side engagement teeth 420a and the second row of floater side engagement teeth 421a and arranging them in a staggered manner, the pitch of the first and second rows of floater side engagement teeth 420a, 421a can be twice the pitch of the valve body side engagement teeth 32, respectively, and a structure is created in which dirt and the like is less likely to adhere or get caught between the first and second rows of floater side engagement teeth 420a, 421a.

<Valve pipe>
13, the valve pipe 5a has a substantially circular inlet opening 50a for attachment to an inlet of a catch basin or the like or an outlet of a pipe (neither of which are shown), and a substantially circular outlet opening 51a that communicates with the inlet opening 50a and forms a valve seat 52a that abuts against the valve body 3a. A groove is provided in the circumferential direction on the outer periphery of the valve pipe 5a, and a packing 53a made of an elastic material such as rubber is fitted into the groove to improve the sealing performance with the inlet of a catch basin or the outlet of a pipe to which the backflow prevention joint 1a is attached.

In the second embodiment, the valve pipe 5a is 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. The diameter of the valve pipe 5a does not necessarily have to be uniform, and it may be configured, for example, as a differential diameter pipe joint in which the diameters of the inlet opening 50a and the outlet opening 51a are different.

In the second embodiment, the outlet opening 51a (valve seat 52a) of the valve pipe 5a is formed vertically (FIG. 10), but may be formed at an incline so as to advance from the upstream side to the downstream side as it moves from top to bottom (not shown). When the outlet opening 51a (valve seat 52a) of the valve pipe 5a is shaped as described above, the rotation angle required for the valve body 3a to close the outlet opening 51a (valve seat 52a) is smaller than when the outlet opening 51a (valve seat 52a) is retreated upstream as it moves from top to bottom, and therefore the occlusion of the outlet opening 51a by the valve body 3a is enhanced.

In addition, in the second embodiment, under normal circumstances, the movement of the valve body 3a is linked to the movement of the floater 4a which tends to descend under its own weight, and the weight of the floater 4a keeps the valve body 3a with the outlet opening 51a (valve seat portion 52a) open, so even if the amount of forward flow drainage is small, a smooth flow of forward flow drainage is guaranteed, and clogging due to foreign matter contained in the drainage does not occur.

As shown in Figures 9, 10, and 13, the upper part of the valve pipe 5a is provided with a hinge support part 54a for rotatably supporting the valve body side hinge part 31a of the valve body 3a and the floater side hinge part 41a of the floater 4a. The shape and number of the hinge support parts 54a are not particularly limited, and the hinge support parts 54a may be divided into a first hinge support part for supporting the valve body side hinge part 31a and a second hinge support part for supporting the floater side hinge part 41.

In the second embodiment, the hinge support part 54a is disposed on the side of the valve body side hinge part 31a so that the axial hole of the hinge support part 54a is aligned with the axial hole of the valve body side hinge part 31a, and the valve body 3a is rotatably supported by inserting one pin O through each axial hole. The hinge support part 54a is disposed on the side of the floater side hinge part 41a above the valve body side hinge part 31a so that the axial hole of the hinge support part 54a is aligned with the axial hole of the floater side hinge part 41a, and the floater 4a is rotatably supported by inserting one pin P through each axial hole.

The configuration of the valve body side hinge part 31a, the floater side hinge part 41a and the hinge support part 54a may be such that a pair of hinge support parts 54a is provided on the valve tube 5a so as to sandwich one valve body side hinge part 31a or one floater side hinge part 41a from both sides as in the second embodiment, or, although not shown, a pair of valve body side hinge parts or a pair of floater side hinge parts may be provided on the valve body or the floater so as to sandwich one hinge support part of the valve tube from both sides. In order to distribute the force acting on the pin as evenly as possible, it is preferable to provide at least two or more of either the valve body side and floater side hinge parts or the hinge support parts.

<Valve body and floater movement>
Fig. 14 is a partial cross-sectional view showing the movement of the valve body 3a and the floater 4a of the backflow prevention joint 1a according to the second embodiment. In Fig. 14, (a) shows the state of the valve body 3a and the floater 4a when basically no backflow water is occurring, and (b) shows the state when the backflow water raises the floater 4a and the valve body 3 closes the outlet opening 51. The movement of the valve body 3a and the floater 4a will be explained below in the order of (a) and (b) of Fig. 14.

<Aspect (a)>
14(a) shows a normal state in which no backflow water is generated in a catch basin or the like to which the backflow prevention joint 1a according to the second embodiment is attached, and only forward flow drainage water flows. In this case, no buoyancy is generated in the buoyancy generating part 40a, and the rotational moment generated in the floater side hinge part 41a due to the weight of the floater 4a is greater than the rotational moment generated in the valve body side hinge part 31a due to the weight of the valve body 3a. Therefore, a downward force is generated in the floater 4a, and the floater side engagement teeth 42a press the valve body side engagement teeth 32a in the direction in which the valve body 3a opens the outlet opening 51a, so that the valve body 3a keeps the outlet opening 51a of the valve pipe 5a open. In other words, the downward movement of the floater 4a connects and links the floater side engagement teeth 42a with the valve body side engagement teeth 32a, and rotates the valve body 3a in the opening direction.

In the embodiment shown in FIG. 14(a), when backflow water or the like occurs and the buoyancy generated in the buoyancy generating portion 40a generates an upward force on the floater 4a, the upward force causes the floater side engagement teeth 42a to press the valve body side engagement teeth 32a in the direction in which the valve body 3a closes the outlet opening 51a. In other words, the floater side engagement teeth 42a engage with the valve body side engagement teeth 32a, so that the valve body 3a reliably closes the outlet opening 51a without malfunctioning. In other words, the upward movement of the floater 4a connects and links the floater side engagement teeth 42a with the valve body side engagement teeth 32a, rotating the valve body 3a in the closing direction.

In this manner, in the embodiment shown in FIG. 14(a), one or more valve body side engagement teeth 32a are provided on the outer periphery of the valve body side hinge portion 31a, and one or more floater side engagement teeth 42a are provided on the outer periphery of the floater side hinge portion 41a. When a downward force is generated on the floater 4a due to its own weight, the downward force causes the floater side engagement teeth 42a to press the valve body side engagement teeth 32a in the direction in which the valve body 3a opens the outlet opening 51a. Therefore, under normal circumstances, the valve body 3a keeps the outlet opening 51a open, ensuring a smooth flow of forward flow drainage even when the amount of forward flow drainage is small, and no clogging occurs due to foreign matter contained in the drainage.

In the backflow prevention joint 1a, if the rotation range of the valve body 3a in the opening direction becomes too large, backflow water may collide with the upstream back surface 34a of the valve body 3a when a backflow occurs, and the valve body 3a may not operate in the closing direction. Therefore, in the second embodiment, when the floater 4a rises, the valve body 3a, which rotates in the direction to open the outlet opening 51a in conjunction with the floater 4a's movement, is configured to abut against the floater 4a, thereby restricting the rotation range of the valve body 3a in the opening direction. In addition, although not shown, the rotation range of the valve body 3a in the opening direction may be restricted by providing a stopper on the hinge support part 54a that supports the valve body side hinge part 31a and engaging the valve body side engagement tooth 32a with the stopper.

In this way, in the second embodiment of the backflow prevention joint 1a, the floater 4a or a dedicated stopper functions as a stopper that restricts the rotation range of the valve body 3a, ensuring that backflow water collides with the downstream surface 33a of the valve body 3a, and ensuring that the valve body 3a rotates to the closing side without malfunctioning due to backflow water.

<Aspect (b)>
14(b) shows a state in which backflow water (not shown) occurs in a catch basin or the like to which the backflow prevention joint 1a according to the second embodiment is attached, and the backflow water raises the floater 4a, causing the valve body 3a to close the outlet opening 51a. In this case, buoyancy is generated in the buoyancy generating part 40a by the backflow water, and the rotational moment generated in the floater side hinge part 41a by the buoyancy of the buoyancy generating part 40a is greater than the rotational moment generated in the floater side hinge part 41a by the weight of the floater 4a, and is greater than the rotational moment generated in the valve body side hinge part 31a by the weight of the valve body 3a. Therefore, a total upward force is generated in the floater 4a, and at this time, the upward force causes the floater side engagement teeth 42 to press the valve body side engagement teeth 32a in the direction in which the valve body 3a closes the outlet opening 51a. In other words, the floater side engagement teeth 42a engage with the valve body side engagement teeth 32a, so the valve body 3a reliably closes the outlet opening 51a without malfunctioning. In other words, the upward movement of the floater 4a connects and links the floater side engagement teeth 42a with the valve body side engagement teeth 32a, rotating the valve body 3a in the closing direction.

In this manner, in the embodiment shown in FIG. 14(b), one or more valve body side engagement teeth 32a are provided on the outer periphery of the valve body side hinge portion 31a, and one or more floater side engagement teeth 42a are provided on the outer periphery of the floater side hinge portion 41a. When an upward force is generated on the floater 4a, the upward force causes the floater side engagement teeth 42a to press the valve body side engagement teeth 32a in the direction in which the valve body 3a closes, so that the valve body 3a reliably closes the outlet opening 51a without malfunction and maintains that state.

As a result, in the embodiment shown in FIG. 14(b), the opening and closing action of the valve body 3a is linked to the movement of the floater 4a, both when the floater 4a descends due to its own weight and when it rises due to the buoyancy generated in the buoyancy generating section 40a.

<Backflow prevention system>
Figure 15 shows an oblique view illustrating an overall overview of a backflow prevention system 2a (partially transparent) relating to a second embodiment of the present invention, and Figure 16 shows a D-D cross-sectional view of the backflow prevention system 2a shown in Figure 15.

As shown in Figures 15 and 16, the second embodiment of the backflow prevention system 2a is constructed by attaching the above-mentioned backflow prevention joint 1a of the present invention to the inlet 61a of a bottomed drainage basin 6a.

More specifically, the drainage manhole 6a used in the backflow prevention system 2a of the second embodiment has a bottom 60a, an inlet 61a that opens horizontally, an outlet 62a that communicates with the inlet 61a and opens horizontally, and an inspection port 63a that communicates with the inlet 61a and the outlet 62a and opens upward. In this embodiment, the inlet 61a, the outlet 62a, and the inspection port 63a all have a receiving port shape, and an upstream connecting pipe 71a, a downstream connecting pipe 72a, and a riser pipe 70a are connected to the inside of each receiving port 61a, 62a, and 63a.

In the second embodiment of the backflow prevention system 2a, the drain manhole 6a, the upstream connecting pipe 71a, the downstream connecting pipe 72a, and the riser pipe 70a are made of polyvinyl chloride resin, but there are no particular limitations on the materials used, and known materials such as plastics can be used.

In the second embodiment of the backflow prevention system 2a, the backflow prevention joint 1a of the present invention is attached by inserting the inlet opening 50a of the backflow prevention joint 1a from inside the drainage manhole 6a into the inlet 61a, and a packing 53a is provided on the outer periphery of the valve pipe 5a, so that the outer periphery of the valve pipe 5a and the inner periphery of the inlet 61a are liquid-tightly sealed, and the backflow prevention joint 1a does not easily fall out of the inlet 61a.

In the second embodiment of the backflow prevention system 2a, the drain manhole 6a is provided with an inspection port 63a that opens upward at the top of the inlet 61a and the outlet 62a, so that the valve body 3a and the floater 4a do not interfere with the drain manhole 6a or the inner wall of the riser pipe 70a, thereby preventing their movement.

According to the second embodiment of the backflow prevention system 2a, the outlet opening 51a of the valve pipe 5a is inclined so as to move forward from the upstream side to the downstream side as it moves vertically or from top to bottom due to the backflow prevention fitting 1a attached to the inlet 61a of the drainage manhole 6a, so that the blocking ability of the valve body 3a is increased when a backflow occurs, and the flow of backflow water can be reliably prevented.

In addition, according to the second embodiment of the backflow prevention system 2a, one or more engagement teeth 32a, 42a are provided on the outer periphery of the hinge part 31a on the valve body side and the outer periphery of the hinge part 41a on the floater side. When a downward force is generated on the floater 4 due to its own weight, the downward force causes the floater side engagement tooth 42a to press the valve body side engagement tooth 32a in the direction in which the valve body 3a opens the outlet opening 51a. Therefore, under normal circumstances, the valve body 3a keeps the outlet opening 51a open, ensuring a smooth flow of forward flow drainage even when the amount of forward flow drainage is small, and preventing clogging due to foreign matter contained in the drainage.

On the other hand, when an upward force is generated on the floater 4a due to the buoyancy generated in the buoyancy generating portion 40a, the upward force causes the floater side engagement tooth 42a to press the valve body side engagement tooth 32a in the direction in which the valve body 3a closes the outlet opening 51a. Therefore, when backflow water occurs, the valve body 3a reliably closes the outlet opening 51a without malfunctioning, preventing the backflow of wastewater.

LIST OF SYMBOLS 1, 1a... Backflow prevention joint 2, 2a... Backflow prevention system 3, 3a... Valve body 30... Packing 31, 31a... Valve body side hinge portion 32, 32a... Valve body side engagement teeth 33, 33a... Downstream side surface 34, 34a... Upstream side back surface 35a... Groove portion 4, 4a... Floater 40, 40a... Buoyancy generating portion 41, 41a... Floater side hinge portion 410... First protrusion portion 411... Second protrusion portion 42, 42a... Floater side engagement teeth 420a... First row of floater side engagement teeth 421a... Second row of floater side engagement teeth 43... Disk portion 44... Cap portion 45a... Rod 5, 5a... Valve pipe 50, 50a... Inlet opening 51, 51a... Outlet opening 52, 52a... Valve seat portion 53, 53a... Packing 54, 54a... Hinge support portion 55... Insertion stopper 6, 6a... Drainage manhole 60, 60a... Bottom portion 61, 61a... Inlet port 62, 62a... Outlet port 63, 63a... Inspection port 70, 70a... Riser pipe 71, 71a... Upstream connecting pipe 72, 72a... Downstream connecting pipe O... Rotation axis of valve body P... Rotation axis of floater

Claims (7)

a valve pipe having an inlet opening and an outlet opening;
a valve body having a valve body side hinge portion rotatably supported by a first hinge support portion provided near the outlet opening of the valve pipe;
A backflow prevention joint comprising: a floater having a buoyancy generating portion and a floater-side hinge portion rotatably supported by a second hinge support portion provided near the outlet opening of the valve pipe,
The valve body side hinge portion is provided with one or more valve body side engagement teeth,
A backflow prevention fitting characterized in that the floater side hinge portion is provided with one or more floater side engagement teeth, and when a downward force is generated on the floater, the downward force causes the floater side engagement teeth to press the valve body side engagement teeth in the direction in which the valve body opens. The backflow prevention joint according to claim 1, characterized in that the range of rotation of the valve body in the opening direction is restricted by the valve body abutting against the floater. The backflow prevention joint according to claim 1, characterized in that when an upward force is generated in the floater, the floater side engagement teeth do not press the valve body side engagement teeth in the direction in which the valve body closes due to the upward force. The backflow prevention joint described in claim 1, characterized in that when an upward force is generated in the floater, the upward force causes the floater side engagement teeth to press the valve body side engagement teeth in the direction in which the valve body closes. a valve pipe having an inlet opening and an outlet opening;
a valve body rotatably supported near an outlet opening of the valve pipe;
a floater having a buoyancy generating portion and rotatably supported in the vicinity of the outlet opening of the valve pipe;
A backflow prevention joint equipped with a connecting means for linking or unlinking the operation of the valve body and the operation of the float, characterized in that the valve body and the float are connected by the connecting means so that the downward movement of the float rotates the valve body in an opening direction, and the backflow prevention joint is unconnected so that the upward movement of the float does not rotate the valve body in a closing direction. A backflow prevention joint according to any one of claims 1 to 5, characterized in that the outlet opening of the valve pipe is inclined so as to progress from the upstream side to the downstream side as it moves vertically or from top to bottom. An inlet opening in a horizontal direction;
A bottomed catch basin having an outlet communicating with the inlet and opening in a horizontal direction, and an inspection hatch communicating with the inlet and the outlet and opening upward,
A backflow prevention system comprising the backflow prevention joint according to claim 6 attached to the inlet.

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