Low resistance backflow preventer

Abstract

The present invention belongs to the field of valve technology and discloses a low-resistance backflow preventer comprising a valve body, a secondary check valve, and a cover plate. The valve body is provided with an inlet chamber, an intermediate chamber, and an outlet chamber, which are sequentially connected along a first direction. The cross-sectional dimensions of the intermediate chamber are larger than those of the inlet chamber and the outlet chamber. The valve body is provided with an inspection port connecting the exterior of the valve body with the intermediate chamber. The secondary check valve is disposed within the intermediate chamber and is capable of entering and exiting the intermediate chamber as a whole along the inspection port. The secondary check valve comprises a cylinder body, a movable plate, a fixing nut, and a sealing assembly. The first end of the cylinder body is configured to abut against the wall of the intermediate chamber at one end near the inlet chamber. The fixing nut is capable of driving the movable plate to abut against the wall of the intermediate chamber at one end near the outlet chamber. The sealing assembly comprises a third sealing ring and a fifth sealing ring. The third sealing ring is disposed on the end face of the first end of the cylinder body, and the fifth sealing ring is disposed on the end face of the movable plate at the end away from the fixing nut. The cover plate is used to seal the inspection port and is detachably connected to the valve body.

Description

Technical Field

[0001] The present invention relates to the technical field of valves, and in particular to a low-resistance backflow preventer. Background Art

[0002] A low-resistance backflow preventer is a non-return device that limits the pressurized water in a pipeline to flow in one direction only. It consists of a secondary check valve and a drain valve. When water flows normally, the secondary check valve is open and the drain valve is closed, allowing water to flow smoothly through the backflow preventer. Once backflow occurs (the outlet pressure increases or the inlet pressure decreases, resulting in the inlet pressure being less than the outlet pressure), the drain valve opens, draining the water from the middle cavity, forming an air barrier, and preventing downstream water from entering the upstream pipeline. Currently, low-resistance backflow preventers used for small-diameter pipelines cannot be repaired online (large-diameter low-resistance backflow preventers that can be repaired online have complex structures and large sizes). The backflow preventer needs to be completely removed from the pipeline before the internal secondary check valve can be repaired. This brings great inconvenience to subsequent inspection and maintenance, greatly increases maintenance costs, prolongs the time of water outages for inspection, and affects users' water use.

[0003] Therefore, a low-resistance backflow preventer is urgently needed to solve the above problems. Summary of the Invention

[0004] The purpose of the present invention is to provide a low-resistance backflow preventer, which does not need to be completely removed from the pipeline during the maintenance process, thereby realizing online maintenance of the low-resistance backflow preventer.

[0005] To achieve this object, the present invention adopts the following technical solutions:

[0006] Low resistance backflow preventer, including:

[0007] a valve body, wherein an inlet cavity, an intermediate cavity, and an outlet cavity are sequentially connected along a first direction, wherein the cross-sectional size of the intermediate cavity is larger than that of the inlet cavity and the outlet cavity, and the valve body is provided with an inspection port connecting the exterior of the valve body with the intermediate cavity;

[0008] and a valve body, wherein the valve body has a first end and a second end, and the valve body has a second end. The valve body has a first end and a second end. The valve body has a second end and a second end. The valve body has a second end and a second end. The valve body has a second end and a second end. The valve body has a second end and a second end. The valve body has a second end and a second end.

[0009] A cover plate is used to block the inspection port, and the cover plate is detachably connected to the valve body.

[0010] Preferably, the secondary check valve further comprises:

[0011] a valve seat disposed at a first end of the cylinder body, wherein an outer wall of the valve seat is sealedly connected to an inner wall of the cylinder body, and a first liquid inlet communicating with the inlet cavity and the accommodating cavity is provided on the valve seat;

[0012] A valve core is slidably arranged in the accommodating chamber, and a first liquid outlet connecting the accommodating chamber and the intermediate chamber is provided on the side wall of the first end of the cylinder body, and a second liquid inlet connecting the intermediate chamber and the accommodating chamber is provided on the side wall of the second end. When the valve core is configured to abut against the valve seat, the valve core blocks the first liquid inlet and the second liquid inlet, and when the valve core is out of abutment with the valve seat, the inlet chamber is connected to the outlet chamber via the accommodating chamber and the intermediate chamber.

[0013] Preferably, the valve core comprises:

[0014] a first valve plate disposed at a first end of the accommodating cavity, the first valve plate being capable of sliding along the accommodating cavity relative to the cylinder body to control the opening and closing of the first liquid inlet;

[0015] a second valve plate disposed at the second end of the accommodating cavity, the second valve plate being capable of sliding along the accommodating cavity relative to the cylinder body to control the opening and closing of the second liquid inlet;

[0016] A valve stem connects the first valve plate and the second valve plate.

[0017] Preferably, the secondary check valve further comprises a sealing assembly, wherein the sealing assembly comprises:

[0018] a first sealing gasket, which is provided on an end surface of the first valve plate close to the valve seat, and when the valve core abuts the valve seat, the first sealing gasket is sandwiched between the first valve plate and the valve seat to seal the gap between the second valve plate and the valve seat;

[0019] a first sealing ring, which is provided on the cavity wall of the accommodating cavity and is located between the first liquid outlet and the second liquid inlet, and is used to seal the gap between the first valve plate and the cavity wall of the accommodating cavity;

[0020] a second sealing gasket, wherein an intermediate partition is provided in the accommodating cavity, the intermediate partition is located between the first liquid outlet and the second liquid inlet, the second sealing gasket is provided on an end surface of the intermediate partition close to the second valve plate, and when the valve core abuts the valve seat, the second sealing gasket is clamped between the second valve plate and the intermediate partition to seal the gap between the second valve plate and the intermediate partition;

[0021] A second sealing ring is provided on the cavity wall of the accommodating cavity and is located on a side of the second liquid inlet close to the outlet cavity, and is used for sealing the gap between the second valve plate and the cavity wall of the accommodating cavity.

[0022] Preferably, the valve core further comprises:

[0023] a first fixing plate detachably connected to an end surface of the first valve plate close to the valve seat, for pressing the first sealing gasket onto the first valve plate, wherein the outer diameter of the first fixing plate is smaller than the outer diameter of the first sealing gasket;

[0024] The second fixing plate is detachably connected to the end surface of the middle partition close to the outlet cavity and is used to press the second sealing gasket onto the middle partition. The outer diameter of the second fixing plate is smaller than that of the second sealing gasket.

[0025] Preferably, the secondary check valve also includes a main spring sleeved on one end of the valve stem close to the inlet cavity, the first valve plate is screwed to the end of the valve stem close to the inlet cavity, one end of the main spring abuts against one side of the first valve plate close to the second valve plate, and the other end abuts against one side of the middle partition plate close to the first valve plate.

[0026] Preferably, the secondary check valve also includes an auxiliary spring sleeved on one end of the valve stem close to the outlet cavity, the second valve plate is slidably sleeved on the valve stem, the end of the auxiliary spring close to the outlet cavity abuts against the first end of the valve stem close to the outlet cavity, and the end of the auxiliary spring away from the outlet cavity abuts against the second valve plate.

[0027] Preferably, the sealing assembly further comprises:

[0028] a fourth sealing ring, which is disposed at the first end of the cylinder body and sandwiched between the cylinder body and the valve seat to seal the gap between the cylinder body and the valve seat;

[0029] A sixth sealing ring is provided on the movable plate and sandwiched between the movable plate and the cylinder body, and is used for sealing the gap between the movable plate and the cylinder body.

[0030] Preferably, the valve body further includes a first detection valve, a second detection valve and a third detection valve arranged on the valve body, the first detection valve is used to detect the liquid pressure in the inlet cavity, the second detection valve is used to detect the liquid pressure in the middle cavity, and the third detection valve is used to detect the liquid pressure in the outlet cavity, and the detection ports of the first detection valve, the second detection valve and the third detection valve are all exposed on the valve body.

[0031] Preferably, it further comprises a drain valve group, which is configured to communicate with the middle cavity to discharge the liquid in the middle cavity when the liquid pressure in the outlet cavity is greater than the liquid pressure in the inlet cavity.

[0032] Beneficial effects of the present invention:

[0033] The low-resistance backflow preventer of the present invention is provided with an inspection port on the valve body, and the secondary check valve can enter and exit the intermediate cavity as a whole along the inspection port. Therefore, when inspecting the low-resistance backflow preventer, the cover plate can be removed, and the fixing nut can be rotated through the inspection port to disengage the movable plate from the cavity wall of the intermediate cavity at one end close to the outlet cavity. At this time, the secondary check valve can be taken out of the intermediate cavity as a whole. When installing the secondary check valve, the secondary check valve is first placed as a whole into the intermediate cavity, and then the first end of the cylinder body is abutted against the cavity wall of the intermediate cavity at one end close to the inlet cavity, and then the fixing nut is rotated to make the movable plate sleeved on the second end of the cylinder body abut against the cavity wall of the intermediate cavity at one end close to the outlet cavity. At this time, the connection between the secondary check valve and the valve body is completed, and disassembly and connection are simple and convenient. Finally, the cover plate can be installed. A third sealing ring, disposed on the end surface of the first end of the cylinder body, is used to seal the gap between the cylinder body and the wall of the intermediate cavity. A fifth sealing ring, disposed on the end surface of the movable plate away from the fixing nut, is used to seal the gap between the movable plate and the wall of the intermediate cavity. The process of connecting the secondary check valve to the valve body is the process of sealing between the secondary check valve and the valve body. When disassembling the secondary check valve, the seal between the secondary check valve and the valve body is released by loosening the fixing nut, eliminating the need to separately disassemble and install the third and fifth sealing rings. The low-resistance backflow preventer does not need to be removed from the pipeline during maintenance, enabling online maintenance of the low-resistance backflow preventer, reducing maintenance time and maintenance costs, shortening water outage time during maintenance, and improving the user's water experience. The combination of the fixing nut and the movable plate to realize the connection and disassembly of the secondary check valve and the valve body is conducive to reducing the size of the secondary check valve, and thus reducing the size of the low-resistance backflow preventer. Moreover, the disassembly and connection of the secondary check valve and the valve body can be completed by rotating the fixing nut, thereby facilitating the disassembly and installation of the secondary check valve in the middle cavity of a small space, so that the low-resistance backflow preventer in this embodiment can be suitable for small-diameter pipelines. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 is a partial cross-sectional view of a low-resistance backflow preventer provided by an embodiment of the present invention;

[0035] Figure 2 This is a schematic diagram of a secondary check valve of a low-resistance backflow preventer provided by an embodiment of the present invention being removed from a valve body;

[0036] Figure 3 2. It is a structural diagram of a secondary check valve of a low-resistance backflow preventer provided by an embodiment of the present invention;

[0037] Figure 4 is a cross-sectional view of a secondary check valve of a low-resistance backflow preventer provided by an embodiment of the present invention;

[0038] Figure 5 This is a schematic diagram of the structure of the cylinder body of the secondary check valve provided by the embodiment of the present invention. Figure 1 ;

[0039] Figure 6 This is a schematic diagram of the structure of the cylinder body of the secondary check valve provided by the embodiment of the present invention. Figure 2 ;

[0040] Figure 7 This is a schematic diagram of the structure of the first valve plate of the secondary check valve provided by an embodiment of the present invention. Figure 1 ;

[0041] Figure 8 This is a schematic diagram of the structure of the first valve plate of the secondary check valve provided by an embodiment of the present invention. Figure 2 ;

[0042] Figure 9 2 is a schematic structural diagram of a second valve plate of a two-stage check valve provided by an embodiment of the present invention;

[0043] Figure 10 Schematic diagram of liquid flow direction of the low-resistance backflow preventer provided by an embodiment of the present invention under normal liquid flow conditions;

[0044] Figure 11 It is a schematic diagram of the liquid flow direction under the backflow prevention working condition of the low-resistance backflow preventer provided by an embodiment of the present invention.

[0045] In the picture:

[0046] 1. Valve body;

[0047] 2. Secondary check valve; 21. Cylinder body; 211. Middle partition; 22. Movable plate; 23. Locking nut; 24. Valve seat; 25. Valve core; 251. First valve plate; 252. Second valve plate; 253. Valve stem; 2531. Shaft shoulder; 254. First fixed plate; 255. Second fixed plate;

[0048] 261, first sealing gasket; 262, first sealing ring; 263, second sealing gasket; 264, second sealing ring; 265, third sealing ring; 266, fourth sealing ring; 267, fifth sealing ring; 268, sixth sealing ring;

[0049] 27. Main spring;

[0050] 28. Auxiliary spring;

[0051] 3. Cover plate;

[0052] 4. First test valve;

[0053] 5. Second detection valve;

[0054] 6. The third test valve;

[0055] 7. Drain valve group;

[0056] 10. Inlet cavity; 20. Middle cavity; 30. Outlet cavity; 40. Inspection port; 50. Accommodation cavity; 60. First liquid inlet; 70. First liquid outlet; 80. Second liquid inlet. DETAILED DESCRIPTION

[0057] The present invention will be further described in detail below with reference to the accompanying drawings and examples. It will be understood that the specific embodiments described herein are intended only to illustrate the present invention and are not intended to limit the present invention. It should also be noted that, for ease of description, the accompanying drawings only illustrate portions relevant to the present invention, not all structures.

[0058] In the description of the present invention, unless otherwise expressly specified or limited, the terms "connected," "connected," and "fixed" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integration; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention in specific circumstances.

[0059] In the present invention, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Furthermore, a first feature being "above," "above," and "above" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature may include the first feature being directly below or obliquely below the second feature, or may simply mean that the first feature is lower in level than the second feature.

[0060] In the description of this embodiment, the terms "upper," "lower," "right," and other orientations or positional relationships are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely for ease of description and simplified operation. They do not indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. Furthermore, the terms "first" and "second" are used solely for descriptive purposes and have no special meanings.

[0061] like Figure 1-3As shown, this embodiment provides a low-resistance backflow preventer, comprising a valve body 1, a secondary check valve 2, and a cover plate 3. The valve body 1 is provided with an inlet cavity 10, an intermediate cavity 20, and an outlet cavity 30, which are sequentially connected along a first direction. The intermediate cavity 20 has a larger cross-sectional dimension than the inlet cavity 10 and the outlet cavity 30. The valve body 1 is provided with an inspection port 40 connecting the exterior of the valve body 1 with the intermediate cavity 20. The secondary check valve 2 is arranged in the middle cavity 20. The secondary check valve 2 can enter and exit the middle cavity 20 as a whole along the inspection port 40. The secondary check valve 2 cooperates with the valve body 1 to check the liquid flowing through the valve body 1. The secondary check valve 2 includes a cylinder 21, a movable plate 22, a fixing nut 23 and a sealing assembly. The first end of the cylinder 21 is configured to abut against the cavity wall of the middle cavity 20 at one end close to the inlet cavity 10. The movable plate 22 and the fixing nut 23 are both sleeved on the second end of the cylinder 21, and the fixing nut 23 is screwed to the cylinder 21. The fixing nut 23 can drive the movable plate 22 to abut against the cavity wall of the middle cavity 20 at one end close to the inlet cavity 10. The movable plate 22 abuts against the wall of the intermediate chamber 20 at one end near the outlet chamber 30. A receiving chamber 50 is provided within the cylinder body 21 for connecting the inlet chamber 10 with the outlet chamber 30. The sealing assembly includes a third sealing ring 265 and a fifth sealing ring 267. The third sealing ring 265 is provided on the end surface of the first end of the cylinder body 21 to seal the gap between the cylinder body 21 and the wall of the intermediate chamber 20. The fifth sealing ring 267 is provided on the end surface of the movable plate 22 away from the fixing nut 23 to seal the gap between the movable plate 22 and the wall of the intermediate chamber 20. The cover plate 3 is used to block the inspection port 40 and is detachably connected to the valve body 1.

[0062] The low-resistance backflow preventer provided in this embodiment is provided with an inspection port 40 on the valve body 1, and the secondary check valve 2 can enter and exit the intermediate cavity 20 as a whole along the inspection port 40. Therefore, when inspecting the low-resistance backflow preventer, the cover plate 3 can be removed, and the fixing nut 23 can be rotated through the inspection port 40 to disengage the movable plate 22 from the cavity wall of the intermediate cavity 20 at one end near the outlet cavity 30. At this time, the secondary check valve 2 can be taken out from the intermediate cavity 20 as a whole. When installing the secondary check valve 2, the secondary check valve 2 is first placed as a whole into the intermediate cavity 20, and then the first end of the cylinder body 21 is abutted against the cavity wall of the intermediate cavity 20 at one end near the inlet cavity 10, and then the fixing nut 23 is rotated to make the movable plate 22 sleeved on the second end of the cylinder body 21 abut against the cavity wall of the intermediate cavity 20 at one end near the outlet cavity 30. At this time, the connection between the secondary check valve 2 and the valve body 1 is completed, and disassembly and connection are simple and convenient. Finally, the cover plate 3 can be installed. A third sealing ring 265, disposed on the end surface of the first end of the cylinder body 21, is used to seal the gap between the cylinder body 21 and the wall of the intermediate chamber 20. A fifth sealing ring 267, disposed on the end surface of the movable plate 22 away from the fixing nut 23, is used to seal the gap between the movable plate 22 and the wall of the intermediate chamber 20. The process of connecting the secondary check valve 2 to the valve body 1 is the process of sealing the secondary check valve 2 and the valve body 1. When disassembling the secondary check valve 2, the seal between the secondary check valve 2 and the valve body 1 is released by loosening the fixing nut 23, eliminating the need to separately disassemble and install the third sealing ring 265 and the fifth sealing ring 267. The low-resistance backflow preventer does not need to be removed from the pipeline during maintenance, enabling online maintenance of the low-resistance backflow preventer, reducing maintenance time and maintenance costs, shortening water outage time during maintenance, and improving the user's water experience. The locking nut 23 cooperates with the movable plate 22 to realize the connection and disassembly of the secondary check valve 2 and the valve body 1, which is beneficial to reducing the size of the secondary check valve 2, and thus reducing the size of the low-resistance backflow preventer. Moreover, the disassembly and connection of the secondary check valve 2 and the valve body 1 can be completed by rotating the locking nut 23, thereby facilitating the disassembly and installation of the secondary check valve 2 in the intermediate cavity 20 of a small space, so that the low-resistance backflow preventer in this embodiment can be suitable for small-diameter pipelines.

[0063] Optionally, steps are provided on both sides of the intermediate cavity 20 along the length direction of the low-resistance backflow preventer. After the secondary check valve 2 is placed in the intermediate cavity 20, the steps support the secondary check valve 2, ensuring that the relative position of the secondary check valve 2 and the valve body 1 is fixed after the secondary check valve 2 is placed in the intermediate cavity 20, and remains coaxial with the opening cavity 10 and the outlet cavity 30.

[0064] Alternatively, as Figure 1-11As shown, the secondary check valve 2 further includes a valve seat 24 and a valve core 25. The valve seat 24 is disposed at the first end of the cylinder body 21. The outer wall of the valve seat 24 is sealedly connected to the inner wall of the cylinder body 21. The valve seat 24 is provided with a first liquid inlet 60 connecting the inlet chamber 10 and the accommodating chamber 50. The valve core 25 is slidably disposed within the accommodating chamber 50. A first liquid outlet 70 connecting the accommodating chamber 50 and the intermediate chamber 20 is provided on the side wall of the first end of the cylinder body 21. A second liquid inlet 80 connecting the intermediate chamber 20 and the accommodating chamber 50 is provided on the side wall of the second end. When the valve core 25 abuts the valve seat 24, it blocks the first and second liquid inlets 60 and 80. When the valve core 25 is no longer in contact with the valve seat 24, the inlet chamber 10 communicates with the outlet chamber 30 via the accommodating chamber 50 and the intermediate chamber 20. That is, the low resistance backflow preventer realizes the connection and disconnection between the inlet chamber 10 and the outlet chamber 30 by the relative sliding of the valve core 25 relative to the cylinder body 21. Specifically, when the liquid pressure in the inlet chamber 10 is greater than the liquid pressure in the outlet chamber 30, the valve core 25 moves along the accommodating chamber 50 in the direction away from the valve seat 24 under the action of the pressure difference between the inlet chamber 10 and the outlet chamber 30, and the valve core 25 is separated from the valve seat 24. At this time, the inlet chamber 10 passes through the first liquid inlet 60, the accommodating chamber 50, the first liquid outlet 70, the intermediate chamber 20, and the second liquid inlet 80 in sequence. The accommodating chamber 50 is connected to the outlet chamber 30, and the liquid entering the inlet chamber 10 can flow smoothly into the outlet chamber 30; when the liquid pressure in the outlet chamber 30 is greater than the liquid pressure in the inlet chamber 10, the valve core 25 moves along the accommodating chamber 50 toward the valve seat 24 under the action of the pressure difference between the inlet chamber 10 and the outlet chamber 30 until it abuts against the valve seat 24. At this time, the valve core 25 blocks the first liquid inlet 60 and the second liquid inlet 80 to disconnect the connection between the inlet chamber 10 and the outlet chamber 20, thereby preventing the liquid from flowing back from the outlet chamber 30 to the inlet chamber 10.

[0065] Alternatively, as Figure 1-11As shown, the valve core 25 includes a first valve plate 251, a second valve plate 252, and a valve stem 253. The first valve plate 251 is disposed at a first end of the accommodating chamber 50 and can slide relative to the cylinder body 21 along the accommodating chamber 50 to control the opening and closing of the first liquid inlet 60. The second valve plate 252 is disposed at a second end of the accommodating chamber 50 and can slide relative to the cylinder body 21 along the accommodating chamber 50 to control the opening and closing of the second liquid inlet 80. The valve stem 253 connects the first valve plate 251 and the second valve plate 252. The valve stem 253 is provided to realize the linkage between the first valve plate 251 and the second valve plate 252. When the first valve plate 251 moves in the direction away from the valve seat 24 to open the first liquid inlet 60, the second valve plate 252 moves along with the first valve plate 251 in the direction away from the valve seat 24 to open the second liquid inlet 80, thereby realizing the connection between the inlet cavity 10 and the outlet cavity 30. When the first valve plate 251 moves in the direction close to the valve seat 24 to close the first liquid inlet 60, the second valve plate 252 moves along with the first valve plate 251 in the direction close to the valve seat 24 to close the second liquid inlet 80.

[0066] Alternatively, as Figure 1 and Figure 4 As shown, the secondary check valve 2 also includes a sealing assembly, which includes a first sealing gasket 261, a first sealing ring 262, a second sealing gasket 263, and a second sealing ring 264. The first sealing gasket 261 is disposed on the end surface of the first valve plate 251 near the valve seat 24. When the valve core 25 abuts the valve seat 24, the first sealing gasket 261 is sandwiched between the first valve plate 251 and the valve seat 24 to seal the gap between the second valve plate 252 and the valve seat 24. The first sealing ring 262 is disposed on the wall of the accommodating chamber 50 and is located between the first liquid outlet 70 and the second liquid inlet 80 to seal the gap between the first valve plate 251 and the wall of the accommodating chamber 50. A middle diaphragm 211 is disposed within the accommodating chamber 50, positioned between the first liquid outlet 70 and the second liquid inlet 80. A second sealing gasket 263 is disposed on the end surface of the middle diaphragm 211 proximal to the second valve plate 252. When the valve core 25 abuts the valve seat 24, the second sealing gasket 263 is sandwiched between the second valve plate 252 and the middle diaphragm 211, thereby sealing the gap between the second valve plate 252 and the middle diaphragm 211. A second sealing ring 264 is disposed on the wall of the accommodating chamber 50, located on the side of the second liquid inlet 80 proximal to the outlet chamber 30, for sealing the gap between the second valve plate 252 and the wall of the accommodating chamber 50. By arranging the first sealing gasket 261, the first sealing ring 262, the second sealing gasket 263 and the second sealing ring 264, when the valve core 25 abuts against the valve seat 24, sealing is achieved between the valve core 25 and the cylinder body 21, as well as between the valve core 25 and the valve seat 24, to ensure that the valve core 25 can well seal the first liquid inlet 60 and the second liquid inlet 80.

[0067] Alternatively, as Figure 4As shown, the valve core 25 further includes a first fixing plate 254 and a second fixing plate 255. The first fixing plate 254 is detachably connected to the end surface of the first valve plate 251 near the valve seat 24 and is used to press the first sealing gasket 261 onto the first valve plate 251. The outer diameter of the first fixing plate 254 is smaller than the outer diameter of the first sealing gasket 261, so that the first sealing gasket 261 is partially exposed from the first fixing plate 254, thereby preventing the first fixing plate 254 from obstructing the contact between the first sealing gasket 261 and the valve seat 25. The second fixing plate 255 is detachably connected to the end surface of the middle partition 211 near the outlet chamber 30 and is used to press the second sealing gasket 263 onto the middle partition 211. The outer diameter of the second fixing plate 255 is smaller than the outer diameter of the second sealing gasket 263, so that the second sealing gasket 263 is partially exposed from the second fixing plate 255, thereby preventing the second fixing plate 255 from obstructing the contact between the second valve plate 252 and the second sealing gasket 263.

[0068] Alternatively, as Figure 4 As shown, a communication hole is provided on the middle partition plate 211 , and the communication hole connects two sides of the middle partition plate 211 , so that the liquid pressure in the outlet cavity 30 can directly act on the first valve plate 251 .

[0069] Alternatively, as Figure 1 and Figure 4 As shown, the two-stage check valve 2 further includes a main spring 27 sleeved around the end of the valve stem 253 near the inlet chamber 10. The first valve plate 251 is threadedly connected to the end of the valve stem 253 near the inlet chamber 10. One end of the main spring 27 abuts the side of the first valve plate 251 near the second valve plate 252, and the other end abuts the side of the intermediate partition 211 near the first valve plate 251. The main spring 27 is used to assist the first raft plate 251 in quickly returning to its original position when the pressure in the outlet chamber 30 exceeds the pressure in the inlet chamber 10, thereby improving the valve core 25's ability to respond to pressure changes in the outlet chamber 30 and the inlet chamber 10.

[0070] Alternatively, as Figure 1 and Figure 4As shown, the secondary check valve 2 also includes an auxiliary spring 28 sleeved on one end of the valve stem 253 close to the outlet chamber 30, and the second valve plate 252 is slidably sleeved on the valve stem 253. The end of the auxiliary spring 28 close to the outlet chamber 30 abuts against the first end of the valve stem 253 close to the outlet chamber 30, and the end of the auxiliary spring 28 away from the outlet chamber 30 abuts against the second valve plate 252. When the liquid pressure in the outlet chamber 30 is greater than the liquid pressure in the inlet chamber 10, the valve core 25 moves toward the valve seat 24 under the combined action of the pressure difference and the main spring 27. When the first valve plate 251 approaches the valve seat 24 but the first sealing gasket 261 has not yet abutted against the valve seat 24, the second valve plate 252 first abuts against the second sealing gasket 263 on the middle partition 211, and the second valve plate 252 slides relative to the valve stem 253. The auxiliary spring 28 begins to compress until the second sealing gasket 261 on the first valve plate 251 abuts against the valve seat 24. During this process, the auxiliary spring 28 acts as a buffer to prevent violent collisions between the first valve plate 251 and the valve seat 24 and between the second valve plate 252 and the middle partition 211, thereby preventing damage to the secondary check valve 2. When the liquid pressure in the inlet chamber 10 is greater than the liquid pressure in the outlet chamber 30, the valve core 25 moves away from the valve seat 24, the main spring 27 compresses, and the auxiliary spring 28 extends, driving the second valve plate 252 to slide relative to the valve stem 253 toward the intermediate partition 211. The valve stem 253 is provided with a shoulder 2531 at the end near the outlet chamber, and the second valve plate 252 returns to a position abutting the shoulder 2531 of the valve stem 253. The elastic coefficient of the auxiliary spring 28 is smaller than that of the main spring 27.

[0071] Alternatively, as Figure 1 and Figure 4 As shown, the sealing assembly further includes a fourth sealing ring 266 and a sixth sealing ring 268. The fourth sealing ring 266 is disposed at the first end of the cylinder body 21 and is sandwiched between the cylinder body 21 and the valve seat 24 to seal the gap between the cylinder body 21 and the valve seat 24. The sixth sealing ring 268 is disposed on the movable plate 22 and is sandwiched between the movable plate 22 and the cylinder body 21 to seal the gap between the movable plate 22 and the cylinder body 21.

[0072] Alternatively, as Figure 1As shown, the low-resistance backflow preventer provided in this embodiment further includes a first detection valve 4, a second detection valve 5, and a third detection valve 6 provided on the valve body 1. The first detection valve 4 is used to detect the liquid pressure in the inlet chamber 10, the second detection valve 5 is used to detect the liquid pressure in the intermediate chamber 20, and the third detection valve 6 is used to detect the liquid pressure in the outlet chamber 30. The detection ports of the first detection valve 4, the second detection valve 5, and the third detection valve 6 are all exposed to the valve body 1. During the operation of the low-resistance backflow preventer, the detection equipment can be connected through the detection ports of the first detection valve 4, the second detection valve 5, and the third detection valve 6 to detect the liquid pressure in the inlet chamber 10, the intermediate chamber 20, and the outlet chamber 30, thereby judging the operation of the low-resistance backflow preventer or testing the backflow prevention performance of the low-resistance backflow preventer.

[0073] Alternatively, as Figure 1 As shown, the low-resistance backflow preventer provided in this embodiment also includes a drain valve assembly 7. This is configured so that when the liquid pressure in the outlet chamber 30 is greater than the liquid pressure in the inlet chamber 10, the drain valve assembly 7 communicates with the intermediate chamber 20 to drain the liquid in the intermediate chamber 20, forming an air barrier and preventing downstream water from entering the upstream pipeline. When the liquid pressure in the inlet chamber 10 is greater than the liquid pressure in the outlet chamber 30, the drain valve assembly 7 disconnects from the intermediate chamber 20, without affecting the normal flow of liquid through the low-resistance backflow preventer.

[0074] Obviously, the above embodiments of the present invention are merely examples for the purpose of clearly illustrating the present invention and are not intended to limit the embodiments of the present invention. A person skilled in the art would be able to make various obvious changes, readjustments, and substitutions without departing from the scope of protection of the present invention. It is not necessary and impossible to enumerate all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the claims of the present invention.

Claims

1. Low resistance backflow preventer, characterized in that: include: A valve body (1) is provided with an inlet cavity (10), an intermediate cavity (20), and an outlet cavity (30) which are sequentially connected along a first direction, wherein the cross-sectional dimension of the intermediate cavity (20) is larger than that of the inlet cavity (10) and the outlet cavity (30), and the valve body (1) is provided with an inspection port (40) which connects the outside of the valve body (1) with the intermediate cavity (20); A secondary check valve (2) is provided in the intermediate cavity (20) and is capable of entering and exiting the intermediate cavity (20) as a whole along the inspection port (40). The secondary check valve (2) cooperates with the valve body (1) to check the liquid flowing through the valve body (1). The secondary check valve (2) comprises a cylinder body (21), a movable plate (22), a fixing nut (23) and a sealing assembly. The first end of the cylinder body (21) is configured to abut against the cavity wall of the intermediate cavity (20) at one end close to the inlet cavity (10). The movable plate (22) and the fixing nut (23) are both sleeved on the second end of the cylinder body (21), and the fixing nut (23) is threadedly connected to the cylinder body (21). The fixing nut (23) can drive the movable plate (22) to abut against the cavity wall of the intermediate cavity (20) at one end close to the inlet cavity (10). The movable plate (22) abuts against the cavity wall of the intermediate cavity (20) at one end close to the outlet cavity (30); a receiving cavity (50) for communicating the inlet cavity (10) and the outlet cavity (30) is provided in the cylinder body (21); the sealing assembly comprises a third sealing ring (265) and a fifth sealing ring (267); the third sealing ring (265) is provided on the end surface of the first end of the cylinder body (21) and is used to seal the gap between the cylinder body (21) and the cavity wall of the intermediate cavity (20); the fifth sealing ring (267) is provided on the end surface of the movable plate (22) away from the fixing nut (23) and is used to seal the gap between the movable plate (22) and the cavity wall of the intermediate cavity (20); A cover plate (3) is used to seal the inspection port (40), and the cover plate (3) is detachably connected to the valve body (1).

2. The low resistance backflow preventer according to claim 1, characterized in that: The secondary check valve (2) further comprises: a valve seat (24) disposed at a first end of the cylinder body (21), the outer wall of the valve seat (24) being sealedly connected to the inner wall of the cylinder body (21), and a first liquid inlet (60) communicating between the inlet cavity (10) and the accommodating cavity (50) being provided on the valve seat (24); A valve core (25) is slidably arranged in the accommodating chamber (50); a first liquid outlet (70) communicating with the accommodating chamber (50) and the intermediate chamber (20) is provided on the side wall of the first end of the cylinder body (21); a second liquid inlet (80) communicating with the intermediate chamber (20) and the accommodating chamber (50) is provided on the side wall of the second end; the valve core (25) is configured to block the first liquid inlet (60) and the second liquid inlet (80) when the valve core (25) abuts against the valve seat (24); and when the valve core (25) is out of abutment with the valve seat (24), the inlet chamber (10) is communicated with the outlet chamber (30) via the accommodating chamber (50) and the intermediate chamber (20).

3. The low resistance backflow preventer according to claim 2, characterized in that: The valve core (25) comprises: a first valve plate (251) disposed at a first end of the accommodating chamber (50), the first valve plate (251) being capable of sliding along the accommodating chamber (50) relative to the cylinder body (21) to control the opening and closing of the first liquid inlet (60); a second valve plate (252) disposed at a second end of the accommodating chamber (50), the second valve plate (252) being capable of sliding along the accommodating chamber (50) relative to the cylinder body (21) to control the opening and closing of the second liquid inlet (80); A valve stem (253) connects the first valve plate (251) and the second valve plate (252).

4. The low resistance backflow preventer according to claim 3, characterized in that: The secondary check valve (2) further comprises a sealing assembly, wherein the sealing assembly comprises: a first sealing gasket (261) disposed on an end surface of the first valve plate (251) close to the valve seat (24); when the valve core (25) abuts against the valve seat (24), the first sealing gasket (261) is sandwiched between the first valve plate (251) and the valve seat (24) to seal a gap between the second valve plate (252) and the valve seat (24); a first sealing ring (262) disposed on the wall of the accommodating cavity (50) and located between the first liquid outlet (70) and the second liquid inlet (80), for sealing the gap between the first valve plate (251) and the wall of the accommodating cavity (50); A second sealing gasket (263), an intermediate partition (211) is provided in the accommodating cavity (50), the intermediate partition (211) is located between the first liquid outlet (70) and the second liquid inlet (80), the second sealing gasket (263) is provided on the end surface of the intermediate partition (211) close to the second valve plate (252), and when the valve core (25) abuts against the valve seat (24), the second sealing gasket (263) is clamped between the second valve plate (252) and the intermediate partition (211) to seal the gap between the second valve plate (252) and the intermediate partition (211); A second sealing ring (264) is provided on the cavity wall of the accommodating cavity (50) and is located on a side of the second liquid inlet (80) close to the outlet cavity (30), and is used to seal the gap between the second valve plate (252) and the cavity wall of the accommodating cavity (50).

5. The low resistance backflow preventer according to claim 4, characterized in that: The valve core (25) further comprises: a first fixing plate (254) detachably connected to an end surface of the first valve plate (251) close to the valve seat (24) and used for pressing the first sealing gasket (261) onto the first valve plate (251); the outer diameter of the first fixing plate (254) is smaller than the outer diameter of the first sealing gasket (261); A second fixing plate (255) is detachably connected to the end surface of the middle partition (211) close to the outlet cavity (30) and is used to press the second sealing gasket (263) onto the middle partition (211). The outer diameter of the second fixing plate (255) is smaller than the outer diameter of the second sealing gasket (263).

6. The low resistance backflow preventer according to claim 4, characterized in that: The secondary check valve (2) further comprises a main spring (27) sleeved on one end of the valve stem (253) close to the inlet chamber (10); the first valve plate (251) is screwed to one end of the valve stem (253) close to the inlet chamber (10); one end of the main spring (27) abuts against one side of the first valve plate (251) close to the second valve plate (252); and the other end abuts against one side of the intermediate partition plate (211) close to the first valve plate (251).

7. The low resistance backflow preventer according to claim 4, characterized in that: The secondary check valve (2) further comprises an auxiliary spring (28) sleeved on one end of the valve stem (253) close to the outlet chamber (30); the second valve plate (252) is slidably sleeved on the valve stem (253); the end of the auxiliary spring (28) close to the outlet chamber (30) abuts against the first end of the valve stem (253) close to the outlet chamber (30); and the end of the auxiliary spring (28) away from the outlet chamber (30) abuts against the second valve plate (252).

8. The low resistance backflow preventer according to claim 4, characterized in that: The sealing assembly further comprises: a fourth sealing ring (266) disposed at a first end of the cylinder (21) and sandwiched between the cylinder (21) and the valve seat (24) to seal a gap between the cylinder (21) and the valve seat (24); A sixth sealing ring (268) is provided on the movable plate (22) and is sandwiched between the movable plate (22) and the cylinder body (21) for sealing the gap between the movable plate (22) and the cylinder body (21).

9. The low resistance backflow preventer according to claim 1, characterized in that: The valve body (1) further comprises a first detection valve (4), a second detection valve (5) and a third detection valve (6), wherein the first detection valve (4) is used to detect the liquid pressure in the inlet chamber (10), the second detection valve (5) is used to detect the liquid pressure in the intermediate chamber (20), and the third detection valve (6) is used to detect the liquid pressure in the outlet chamber (30). The detection ports of the first detection valve (4), the second detection valve (5) and the third detection valve (6) are all exposed to the valve body (1).

10. The low resistance backflow preventer according to claim 1, characterized in that: The invention also includes a drain valve group (7), wherein the drain valve group (7) is configured such that when the liquid pressure in the outlet cavity (30) is greater than the liquid pressure in the inlet cavity (10), the drain valve group (7) is connected to the intermediate cavity (20) to discharge the liquid in the intermediate cavity (20).

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