Low-resistance backflow preventer

Abstract

The invention belongs to the technical field of backflow preventers, and discloses a low-resistance backflow preventer which comprises a valve body and a check valve, and the valve body is sequentially communicated with an inlet cavity, a middle cavity and an outlet cavity in the first direction; the check valve comprises a cylinder body, a water inlet check valve piece and a water outlet check valve piece, the cylinder body is fixed in the middle cavity, and the cylinder body is provided with a water inlet communicated with the inlet cavity and a water outlet communicated with the outlet cavity; a first limiting part, a second limiting part and a third limiting part are sequentially arranged in the cylinder body in the first direction, and the water inlet check valve piece is connected to the third limiting part through a first elastic piece and slides between the first limiting part and the second limiting part. The water inlet check valve can abut against the first limiting part in a sealed mode. The water outlet check valve piece is connected to the third limiting part through a second elastic piece and slides between the water inlet check valve piece and the third limiting part, so that the stability of the low-resistance backflow preventer is improved.

Description

Technical Field

[0001] This invention relates to the field of backflow prevention technology, and more particularly to a low-resistance backflow prevention device. Background Technology

[0002] The low-resistance backflow preventer is a hydraulic combination device that prevents the medium at the inlet end from being contaminated by backflow. It mainly consists of two-stage check valves and a drain valve. When the water is flowing normally, the pressure at the inlet end is greater than the pressure at the outlet end. The two-stage check valves open and the drain valve closes, allowing the water to flow normally through the low-resistance backflow preventer. Once the pressure at the outlet end is greater than the pressure at the inlet end, the drain valve opens and the two-stage inlet valves close, preventing downstream water from flowing back.

[0003] In related technologies, most low-resistance backflow preventers adopt a structure in which two-stage check valve plates are installed on a valve stem. As a result, when either stage check valve becomes stuck, the other stage check valve will also be unable to close, thus causing backflow contamination and reducing the stability of the low-resistance backflow preventer. Summary of the Invention

[0004] The purpose of this invention is to provide a low-resistance backflow preventer to improve the stability of the low-resistance backflow preventer.

[0005] To achieve this objective, the present invention adopts the following technical solution:

[0006] Low-resistance backflow preventer, comprising:

[0007] The valve body is sequentially connected to an inlet chamber, an intermediate chamber, and an outlet chamber along a first direction;

[0008] A check valve, comprising a cylinder body, an inlet check valve component, and an outlet check valve component, wherein the cylinder body is fixed in the intermediate cavity, and the cylinder body has an inlet communicating with the inlet chamber and an outlet communicating with the outlet chamber.

[0009] The cylinder body is provided with a first limiting part, a second limiting part, and a third limiting part in sequence along the first direction. The inlet check valve is connected to the third limiting part through a first elastic member and slides between the first limiting part and the second limiting part. The inlet check valve can seal against the first limiting part to block the inlet and the outlet. The outlet check valve is connected to the third limiting part through a second elastic member and slides between the inlet check valve and the third limiting part. The outlet check valve can seal against the inlet check valve to block the inlet and the outlet.

[0010] When the inlet check valve is disengaged from the first limiting part, the water flow can pass over the inlet check valve and flow to the outlet check valve, pushing the outlet check valve to disengage from the inlet check valve, so that the water flow passes over the outlet check valve and flows to the outlet.

[0011] In some embodiments, the first limiting part is an annular valve seat disposed on the cylinder body, and a first sealing ring is disposed on the side of the annular valve seat facing the water inlet check valve.

[0012] In some embodiments, a second sealing ring is provided on the side of the inlet check valve facing the outlet check valve and / or on the side of the outlet check valve facing the inlet check valve.

[0013] In some embodiments, the inlet check valve is provided with a removable pressure plate, and the second sealing ring is pressed against the inlet check valve by the pressure plate.

[0014] In some embodiments, the outer periphery of the outlet check valve protrudes beyond the outer periphery of the inlet check valve, a third sealing ring is clamped between the outer peripheral wall of the outlet check valve and the inner wall of the cylinder, and a flow hole is provided on the outlet check valve.

[0015] In some embodiments, there is a flow gap between the outer peripheral wall of the inlet check valve and the inner wall of the cylinder.

[0016] In some embodiments, both the first elastic member and the second elastic member are springs, and the second elastic member is sleeved on the outside of the first elastic member.

[0017] In some embodiments, the valve body is provided with a maintenance port communicating with the intermediate cavity, the low-resistance backflow preventer is provided with a valve cover, the valve cover is detachably connected to the valve body to open or close the maintenance port, and the check valve is detachably connected to the valve body.

[0018] In some embodiments, the low-resistance backflow preventer further includes a drainer, which includes a drain housing with two partitions inside. The partitions are deformable to divide the drain housing into a first cavity, a second cavity, and a third cavity. The first cavity is connected to the inlet cavity, the second cavity is connected to the intermediate cavity, and the third cavity is connected to the outlet cavity. The drain housing also has a drain outlet that connects the second cavity to the external space. A blocking block is provided on the partition separating the first cavity to block the drain outlet. The two partitions are connected by a connecting rod.

[0019] In some embodiments, the drain further includes an adjusting rod inserted into the first cavity, the adjusting rod being movable in the direction of entering and exiting the first cavity to abut or disengage from the partition, thereby bringing the sealing block closer to or away from the drain outlet.

[0020] The beneficial effects of this invention are:

[0021] In the initial state, the outlet check valve rests against the inlet check valve, which in turn rests against the first limiting part. During normal water supply, the pressure at the inlet is greater than the pressure at the outlet. The water flow pushes both the inlet and outlet check valves together in the first direction. The inlet check valve disengages from the first limiting part, opening the seal between them. The water flow passes over the inlet check valve and acts on the outlet check valve. Simultaneously, due to the movement of the inlet check valve, the first elastic element accumulates potential energy. As the water flow acts on the outlet check valve, the inlet check valve is limited by the second limiting part, while the outlet check valve is moved away from the inlet check valve by the water flow. Thus, the water flow can pass over the outlet check valve and flow out from the outlet to the outlet cavity, achieving normal water discharge. During this process, the second elastic element accumulates potential energy due to the movement of the outlet check valve. When the water pressure at the outlet is greater than the pressure at the inlet... When the water pressure at the inlet is high, the water flow at the outlet acts on the inlet and outlet check valves. Under the combined action of the water flow and the second elastic element, the outlet check valve abuts against the inlet check valve and, together with the water flow and the first elastic element, pushes the inlet check valve against the first limiting part, preventing water from flowing back to the inlet. At the same time, the outlet check valve abutting against the inlet check valve at the first limiting part also improves the sealing performance. Even if the inlet check valve is stuck, the seal between the outlet and inlet check valves can still prevent water from flowing back. Even if the outlet check valve is stuck, the water flow and the first elastic element can still act on the inlet check valve, pushing it against the first limiting part and preventing water from flowing back. Thus, even if either the inlet or outlet check valve is stuck, it can still prevent water from flowing back, thereby improving the stability of the low-resistance backflow preventer. Attached Figure Description

[0022] Figure 1 This is a schematic diagram showing the inlet check valve and outlet check valve in contact as described in an embodiment of the present invention;

[0023] Figure 2 This is a schematic diagram of the outlet check valve detaching from the inlet check valve according to an embodiment of the present invention;

[0024] Figure 3 This is a schematic diagram of the cylinder block according to an embodiment of the present invention;

[0025] Figure 4 This is a diagram showing the water flow direction during water discharge as described in an embodiment of the present invention;

[0026] Figure 5 This is a water flow direction diagram for preventing backflow of water as described in an embodiment of the present invention;

[0027] Figure 6 This is a schematic diagram of the valve cover detaching from the valve body according to an embodiment of the present invention.

[0028] In the picture:

[0029] 1. Valve body; 11. Inlet chamber; 12. Intermediate chamber; 13. Outlet chamber; 14. Maintenance port;

[0030] 2. Check valve; 21. Cylinder body; 201. First cylinder body ring; 202. Second cylinder body ring; 203. Connecting rib; 22. Inlet check valve component; 23. Outlet check valve component; 24. Inlet; 25. Outlet; 26. First limiting part; 27. Second limiting part; 28. Third limiting part; 29. ​​First elastic element; 210. Second elastic element; 211. First sealing ring; 212. Second sealing ring; 214. Pressure plate; 215. Third sealing ring; 216. Fourth sealing ring; 217. Fifth sealing ring;

[0031] 3. Valve cover;

[0032] 4. Drainage device; 41. Drainage housing; 42. Divider; 43. First chamber; 44. Second chamber; 45. Third chamber; 46. Drain outlet; 47. Blocking block; 48. Connecting rod; 49. Adjusting rod;

[0033] 5. Tighten the nut. Detailed Implementation

[0034] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar components or components having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0035] In the description of this invention, unless otherwise explicitly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection or a detachable connection; a mechanical connection or an electrical connection; a direct connection or an indirect connection through an intermediate medium; or the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0036] In the description of this invention, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0037] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0038] like Figures 1 to 6 As shown, the present invention provides a low-resistance backflow preventer, which includes a valve body 1 and a check valve 2. The valve body 1 is sequentially connected to an inlet chamber 11, an intermediate chamber 12, and an outlet chamber 13 along a first direction. The check valve 2 includes a cylinder 21, an inlet check valve component 22, and an outlet check valve component 23. The cylinder 21 is fixed in the intermediate chamber 12 and has an inlet 24 connected to the inlet chamber 11 and an outlet 25 connected to the outlet chamber 13. A first limiting part 26, a second limiting part 27, and a third limiting part 28 are sequentially arranged inside the cylinder 21 along the first direction. The inlet check valve component 22 is connected to the third limiting part 28 through a first elastic member 29 and slides between the first limiting part 26 and the second limiting part 28. Between the positions 27; the inlet check valve 22 can seal against the first limiting part 26 to block the inlet 24 and the outlet 25; the outlet check valve 23 is connected to the third limiting part 28 through the second elastic member 210 and slides between the inlet check valve 22 and the third limiting part 28, and the outlet check valve 23 can seal against the inlet check valve 22 to block the inlet 24 and the outlet 25; when the inlet check valve 22 is disengaged from the first limiting part 26, the water flow can pass over the inlet check valve 22 and flow to the outlet check valve 23, and push the outlet check valve 23 to disengage from the inlet check valve 22, so that the water flow passes over the outlet check valve 23 and flows to the outlet 25.

[0039] The low-resistance backflow preventer provided in this embodiment, in its initial state, has the outlet check valve 23 abutting against the inlet check valve 22, and the inlet check valve 22 abutting against the first limiting part 26. During normal water supply, the pressure at the inlet 24 is greater than the pressure at the outlet 25, and the water flow can push the inlet check valve 22 and the outlet check valve 23 to move together in the first direction. The inlet check valve 22 disengages from the first limiting part 26, the seal between them is opened, and the water flow passes over the inlet check valve 22 and acts on the outlet... The water check valve 23, and simultaneously due to the movement of the inlet check valve 22, the first elastic element 29 accumulates potential energy. As the water flow acts on the outlet check valve 23, the inlet check valve 22 is limited by the second limiting part 27, and the outlet check valve 23 is moved away from the inlet check valve 22 by the water flow, so that the water flow can pass over the outlet check valve 23 and flow out from the outlet 25 to the outlet cavity 13, realizing normal water discharge. At the same time, due to the movement of the outlet check valve 23, the second elastic element 210 accumulates potential energy; and when the outlet... When the water pressure at outlet 25 is greater than the water pressure at inlet 24, the water flow at outlet 25 acts on inlet check valve 22 and outlet check valve 23. Under the action of the water flow and the second elastic member 210, outlet check valve 23 abuts against inlet check valve 22, and can, together with the water flow and the first elastic member 29, push inlet check valve 22 against the first limiting part 26, preventing water from flowing back to inlet 24. Even if inlet check valve 22 is stuck, the distance between outlet check valve 23 and inlet check valve 22 remains constant. The seal can still prevent water backflow; at the same time, the outlet check valve 23 abutting against the inlet check valve 22 at the first limiting part 26 can also improve the sealing performance; even if the outlet check valve 23 is stuck, the water flow and the first elastic member 29 can also act on the inlet check valve 22, pushing the inlet check valve 22 against the first limiting part 26 to prevent water backflow. Thus, even if either the inlet check valve 22 or the outlet check valve 23 is stuck, the function of preventing water backflow can be achieved, thereby improving the stability of the low-resistance backflow preventer.

[0040] like Figure 2 As shown, in some embodiments, the first limiting part 26 is an annular valve seat disposed on the cylinder body 21. The annular valve seat can be connected to the cylinder body 21 by means of, but not limited to, snap-fit ​​or plug-in connection. A first sealing ring 211 is provided on the side of the annular valve seat facing the inlet check valve 22, so that the inlet check valve 22 can press against the first sealing ring 211 to achieve a seal when it contacts the annular valve seat. Specifically, a first groove is provided on the side of the annular valve seat facing the inlet check valve 22, and the first sealing ring 211 is embedded in the first groove and protrudes from the first groove. Exemplarily, the first sealing ring 211 can be, but is not limited to, a rubber ring.

[0041] In order to allow water flow to pass over the inlet check valve 22 after it is disengaged from the first limiting part 26, in the current embodiment, there is a flow gap between the outer peripheral wall of the inlet check valve 22 and the inner wall of the cylinder 21.

[0042] like Figure 3 As shown, specifically, the cylinder body 21 includes a first cylinder body ring 201 and a second cylinder body ring 202. The first cylinder body ring 201 and the second cylinder body ring 202 are spaced apart along a first direction. The first cylinder body ring 201 and the second cylinder body ring 202 are connected by a plurality of circumferentially spaced connecting ribs 203. An annular valve seat is disposed inside the first cylinder body ring 201. The second limiting part 27 is an annular protrusion disposed on the connecting rib 203. The above-mentioned flow gap is formed between adjacent connecting ribs 203, so that after the inlet check valve 22 is disengaged from the first limiting part 26, the water flow can pass over the inlet check valve 22.

[0043] In the current embodiment, the inlet check valve 22 includes an inlet baffle plate, an inlet ring wall arranged circumferentially on the inlet baffle plate, and a sliding ring on the outer side of the inlet ring wall. The sliding ring abuts against the connecting rib 203 and slides between the first limiting part 26 and the second limiting part 27. Water can enter through the inlet 24 and act on the inlet baffle plate, thereby causing the sliding ring to slide away from the first limiting part 26.

[0044] like Figure 2 As shown, in some embodiments, the outer periphery of the outlet check valve 23 protrudes beyond the outer periphery of the inlet check valve 22. Thus, when the inlet check valve 22 disengages from the first sealing ring 211, the water flow can pass through the flow gap to the outlet check valve 23, thereby pushing the outlet check valve 23 away from the inlet check valve 22, so that the water flow is located between the inlet check valve 22 and the outlet check valve 23. In order for the water flow to pass through the outlet check valve 23, a flow hole is provided on the outlet check valve 23 so that the water flow can pass through. When the water pressure at the outlet 25 is greater than that at the inlet 24, the water flow can directly act on the inlet check valve 22 through the flow hole. A third sealing ring 215 is held between the outer peripheral wall of the outlet check valve 23 and the inner wall of the cylinder 21, thereby preventing water from flowing directly from the outlet 25 through the space between the outlet check valve 23 and the inner wall of the cylinder 21 to the inlet 24. For example, the outer peripheral wall of the outlet check valve 23 is provided with a second groove, in which the third sealing ring 215 is embedded to seal the gap between the outer peripheral wall of the outlet check valve 23 and the inner wall of the cylinder 21.

[0045] In the current embodiment, the outlet check valve 23 slides within the second cylinder ring 202, and the third sealing ring 215 contacts the inner wall of the second cylinder ring 202 to form a seal. Since the outer periphery of the outlet check valve 23 protrudes beyond the outer periphery of the inlet check valve 22, and the cylinder 21 has a large-diameter section and a small-diameter section at the connecting rib 203, the sliding ring of the inlet check valve 22 slides in the small-diameter section, while the outlet check valve 23 moves in the large-diameter section. It should also be noted that the second limiting part 27 is a protruding ring located in the small-diameter section.

[0046] In the current embodiment, the outlet check valve 23 includes an outlet baffle plate, the outlet baffle plate is provided with the aforementioned flow hole, the outlet baffle plate is provided with an outlet ring wall, the outlet ring wall is arranged around the flow hole, and the third sealing ring 215 is arranged on the outer periphery of the outlet ring wall so that the outlet ring wall and the inner wall of the second cylinder ring 202 form a sliding seal.

[0047] In some embodiments, in order to form a seal between the inlet check valve 22 and the outlet check valve 23, a second sealing ring 212 is provided on the side of the inlet check valve 22 facing the outlet check valve 23 and / or on the side of the outlet check valve 23 facing the inlet check valve 22. In the current embodiment, in order to facilitate the connection of the second sealing ring 212, a detachable pressure plate 214 is provided on the side of the inlet check valve 22 facing the outlet check valve 23. The pressure plate 214 can be, but is not limited to, connected to the inlet check valve 22 by bolts, and the second sealing ring 212 is pressed onto the inlet check valve 22 by the pressure plate 214.

[0048] like Figure 2 As shown, in some embodiments, both the first elastic element 29 and the second elastic element 210 are springs, with the second elastic element 210 sleeved on the outside of the first elastic element 29, thereby reducing space occupation. To facilitate the placement of the first elastic element 29 and the second elastic element 210, ensuring that the inlet check valve 22 and the outlet check valve 23 can return to their initial states via the second elastic element 210 and the first elastic element 29 respectively after water pressure loss, the third limiting part 28 is an outlet grille disposed within the second cylinder ring 202. One end of the first elastic element 29 and one end of the second elastic element 210 are both connected to the outlet grille, and the other end of the first elastic element 29 is connected to the inlet baffle plate; the other end of the second elastic element 210 is connected to the outlet baffle plate. Exemplarily, the outlet grille may, but is not limited to, be integrally formed with the cylinder 21.

[0049] like Figure 6As shown, in some embodiments, for ease of maintenance, the valve body 1 is provided with a maintenance port 14 communicating with the intermediate cavity 12, the low resistance backflow preventer is provided with a valve cover 3, the valve cover 3 is detachably connected to the valve body 1 so as to open or close the maintenance port 14, and the check valve 2 is detachably connected to the valve body 1 so as to remove the check valve 2 from the valve body 1 for maintenance. In the current embodiment, the size of the intermediate cavity 12 is larger than that of the inlet cavity 11 and the outlet cavity 13. A fourth sealing ring 216 is provided on one end face of the cylinder body 21 along the first direction, so that the cylinder body 21 abuts against the cavity wall of one side of the intermediate cavity 12 along the first direction through the fourth sealing ring 216. The cylinder body 21 is also provided with threads, and a locking nut 5 is screwed to the cylinder body 21 through the threads. A fifth sealing ring 217 is clamped between the locking nut 5 and the other cavity wall of the intermediate cavity 12. Thus, by turning the locking nut 5, the locking nut 5 can abut against the fifth sealing ring 217. In the process of turning the locking nut 5, the cylinder body 21 is pushed to move away from the fifth sealing ring 217 along the first direction, so that the cylinder body 21 clamps the fourth sealing ring 216 with the valve body 1 to form a seal and fix the cylinder body 21. When maintenance is required, the locking nut 5 can be turned in the opposite direction, making the disassembly and fixation of the cylinder body 21 more convenient.

[0050] like Figure 1 , Figure 4 and Figure 5As shown, in some embodiments, the backflow preventer further includes a drain 4, which includes a drain housing 41. Two spaced-apart partitions 42 are disposed within the drain housing 41 along a first direction. Both partitions 42 are connected to the drain housing 41 and are deformable. A connecting rod 48 connects the two partitions 42. The two partitions 42 divide the drain housing 41 into a first cavity 43, a second cavity 44, and a third cavity 45 along the first direction. The first cavity 43 connects to the inlet cavity 11, the second cavity 44 connects to the intermediate cavity 12, and the third cavity 45 connects to the outlet cavity 13. Thus, water flowing from the inlet cavity 11 can enter the first cavity 43, water flowing from the intermediate cavity 12 can enter the intermediate cavity 12, and water flowing from the outlet cavity 13 can enter the third cavity 45. The drain housing 41 is also provided with a surface facing the first cavity 43. The drain outlet 46 of the partition plate 42 connects the second cavity 44 and the external space. At the same time, the partition plate 42, which is used to separate the first cavity 43, is provided with a blocking block 47, which blocks the drain outlet 46. The connecting rod 48 passes through the blocking block 47 and connects the two partition plates 42. Thus, when the water pressure at the inlet 24 is greater than the water pressure at the outlet 25, the water pressure in the first cavity 43 is greater than the water pressure in the third cavity 45. The partition plate 42 will drive the blocking block 47 to block the drain outlet 46. Since the drain outlet 46 is blocked, when the water pressure at the outlet 25 is greater than the water pressure at the inlet 24, the water pressure in the third cavity 45 is greater than the water pressure in the first cavity 43. The blocking block 47 will be driven by the connecting rod 48 to move away from the drain outlet 46, thus opening the drain outlet 46. The water flow from the outlet 25 will flow out through the intermediate cavity 12 and out of the drain outlet 46, realizing emergency drainage.

[0051] In some embodiments, the drainer 4 further includes an adjusting rod 49, which is screwed onto the drain housing 41 and extends into the first cavity 43. By turning the adjusting rod 49, it can be moved in the direction of entering and exiting the first cavity 43, abutting against the partition plate 42, thereby moving the sealing block 47 closer to or away from the drain outlet 46. In the current embodiment, the connecting rod 48 passes through and is fixedly connected to the partition plate 42 separating the first cavity 43. The adjusting rod 49 abuts against the connecting rod 48, thereby moving the connecting rod 48 and causing the sealing block 47 to move closer to or away from the drain outlet 46. Therefore, when it is necessary to urgently close the drain outlet 46, simply turning the adjusting rod 49 is sufficient.

[0052] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A low-resistance backflow preventer, characterized in that, include: The valve body (1) is connected in sequence along the first direction to the inlet cavity (11), the intermediate cavity (12) and the outlet cavity (13); Check valve (2), the check valve (2) includes cylinder body (21), inlet check valve component (22) and outlet check valve component (23), the cylinder body (21) is fixed in the intermediate cavity (12), the cylinder body (21) has an inlet (24) communicating with the inlet cavity (11) and an outlet (25) communicating with the outlet cavity (13); The cylinder body (21) is provided with a first limiting part (26), a second limiting part (27) and a third limiting part (28) in sequence along the first direction. The inlet check valve (22) is connected to the third limiting part (28) through a first elastic member (29) and slides between the first limiting part (26) and the second limiting part (27). The inlet check valve (22) can seal against the first limiting part (26) to block the inlet (24) and the outlet (25). The outlet check valve (23) is connected to the third limiting part (28) through a second elastic member (210) and slides between the inlet check valve (22) and the third limiting part (28). The outlet check valve (23) can seal against the inlet check valve (22) to block the inlet (24) and the outlet (25). When the inlet check valve (22) disengages from the first limiting part (26), the water flow can pass over the inlet check valve (22) and flow to the outlet check valve (23), and push the outlet check valve (23) to disengage from the inlet check valve (22), so that the water flow passes over the outlet check valve (23) and flows to the outlet (25).

2. The low-resistance backflow preventer according to claim 1, characterized in that, The first limiting part (26) is an annular valve seat provided on the cylinder body (21), and a first sealing ring (211) is provided on the side of the annular valve seat facing the water inlet check valve (22).

3. The low-resistance backflow preventer according to claim 1, characterized in that, The inlet check valve (22) is provided with a second sealing ring (212) on the side facing the outlet check valve (23) and / or the outlet check valve (23) is provided with a second sealing ring (212) on the side facing the inlet check valve (22).

4. The low-resistance backflow preventer according to claim 3, characterized in that, The inlet check valve (22) is provided with a detachable pressure plate (214), and the second sealing ring (212) is pressed onto the inlet check valve (22) by the pressure plate (214).

5. The low-resistance backflow preventer according to claim 1, characterized in that, The outer periphery of the outlet check valve (23) protrudes from the outer periphery of the inlet check valve (22), and a third sealing ring (215) is clamped between the outer periphery of the outlet check valve (23) and the inner wall of the cylinder (21). A flow hole is provided on the outlet check valve (23).

6. The low-resistance backflow preventer according to claim 1, characterized in that, There is a flow gap between the outer peripheral wall of the inlet check valve (22) and the inner wall of the cylinder (21).

7. The low-resistance backflow preventer according to claim 1, characterized in that, Both the first elastic element (29) and the second elastic element (210) are springs, with the second elastic element (210) sleeved on the outside of the first elastic element (29).

8. The low-resistance backflow preventer according to any one of claims 1-7, characterized in that, The valve body (1) is provided with a maintenance port (14) that connects to the intermediate cavity (12). The low-resistance backflow preventer is provided with a valve cover (3). The valve cover (3) is detachably connected to the valve body (1) to open or close the maintenance port (14). The check valve (2) is detachably connected to the valve body (1).

9. The low-resistance backflow preventer according to any one of claims 1-7, characterized in that, The low-resistance backflow preventer also includes a drainer (4), which includes a drain housing (41). The drain housing (41) is provided with two partitions (42) to divide the drain housing (41) into a first cavity (43), a second cavity (44) and a third cavity (45). The first cavity (43) is connected to the inlet cavity (11), the second cavity (44) is connected to the intermediate cavity (12), and the third cavity (45) is connected to the outlet cavity (13). The partitions (42) are deformable. The drain housing (41) is also provided with a drain outlet (46), which is connected to the second cavity (44) and the external space. A blocking block (47) is provided on the partitions (42) that separate the first cavity (43). The blocking block (47) is used to block the drain outlet (46). The two partitions (42) are connected by a connecting rod (48).

10. The low-resistance backflow preventer according to claim 9, characterized in that, The drainer (4) also includes an adjusting rod (49) which is inserted into the first cavity (43). The adjusting rod (49) can be moved and adjusted in the direction of entering and exiting the first cavity (43) to abut or disengage from the partition plate (42) so that the sealing block (47) is close to or away from the drain outlet (46).

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