A backflow preventer

Abstract

The present invention belongs to the field of check valves and specifically discloses a backflow preventer; the inner cavity of the backflow preventer housing is divided into a first chamber and a second chamber; the sensing cavity in the first chamber forms a sensing cavity with the inlet valve disc and is connected via an inlet reset member; one side of the first chamber is connected to the water inlet, and the other side is connected to the second chamber via a connecting channel; the second chamber is connected to the water outlet and is connected to the sensing cavity via a backflow channel; the inlet valve disc is sealed with the inlet valve seat at the water inlet, and the outlet valve disc is sealed with the outlet valve seat at the connecting channel; when backflow occurs, the fluid enters the second chamber from the water outlet and closes the outlet valve disc, and at the same time flows into the sensing cavity; the inlet valve disc is closed under the combined action of the fluid pressure in the sensing cavity and the inlet reset member, thereby preventing the fluid from flowing back. Due to the introduction of fluid into the sensing cavity, the resistance characteristics of the inlet valve disc are changed, which can effectively reduce water loss and improve the reliability of the backflow preventer.

Description

Technical Field

[0001] The present invention belongs to the technical field of check valves, and more particularly, relates to a backflow preventer. Background Art

[0002] Backflow preventer is an important component used to prevent the backflow of water or media with physical and chemical properties similar to water, thereby protecting the pipeline system. Due to its high safety performance, small size and sensitive action, it has become the preferred product for preventing backflow pollution in pipelines.

[0003] Backflow preventers generally prevent fluid backflow by installing two check valves at the inlet and outlet ends. There are two types of backflow preventers in the prior art: one is a linked valve flap type backflow preventer, in which the two valve flaps of the backflow preventer are linked (the inlet valve flap and the outlet valve flap move together, opening and closing at the same time). The disadvantage of this backflow preventer is that when one valve flap becomes stuck or fails, the other valve flap cannot be closed safely and reliably, so the reliability of this backflow preventer is low. At the same time, this backflow preventer requires the design of a linkage mechanism, which makes its production and assembly more complicated. The other is an independent check valve backflow preventer, in which the two valve flaps of the backflow preventer move independently, avoiding the low reliability problem of the linked valve flap type backflow preventer and reducing the difficulty of production and assembly. However, when backflow occurs, the inlet check valve is subject to large fluid resistance, and the spring force needs to be increased to overcome the fluid resistance and close the inlet check valve. However, increasing the spring force leads to excessive water loss in the entire machine.

[0004] In the prior art, there are backflow preventers with independent check valves. For example, document 202110745351.5 discloses a low-water-loss backflow preventer. This device equips the inlet check valve with a magnetic assembly, which closes the inlet check valve under the combined action of magnetic and spring forces, thereby reducing water loss. However, the addition of the magnetic assembly makes the backflow preventer more complex.

[0005] Based on the above defects and shortcomings, the field urgently needs to make further improved designs for the existing backflow preventers to overcome the low reliability problem of the linked valve flap type backflow preventer in the prior art and the large water loss problem of the independent check valve backflow preventer, and provide a backflow preventer with high reliability, low water loss and simple processing and assembly. Summary of the Invention

[0006] In response to the above defects or improvement needs of the prior art, the present invention provides a backflow preventer to overcome the problem of low reliability of the linked valve flap type backflow preventer in the prior art and the problem of large water loss of the backflow preventer of the independent check valve, while solving the problem of complex structure of the existing backflow preventer, and providing a backflow preventer with high reliability, low water loss and simple processing and assembly, which is particularly suitable for the application of the backflow preventer.

[0007] To achieve the above-mentioned object, the present invention proposes a backflow preventer, which includes a housing, an inlet valve seat, an inlet valve disc, an outlet valve seat, an outlet valve disc, and a water inlet and a water outlet provided at both ends of the housing;

[0008] The inner cavity of the shell is divided into a first chamber and a second chamber; one side of the first chamber is connected to the water inlet, and the other side is connected to the second chamber through a connecting channel; a sensing cavity is provided inside the first chamber, and the sensing cavity is provided with an opening facing the water inlet; the second chamber is connected to the water outlet on the side away from the connecting channel;

[0009] The inlet valve seat is set at the water inlet;

[0010] The inlet valve flap is slidably and sealingly connected to the opening of the sensing cavity and is connected to the sensing cavity via an inlet reset member, so that the inlet valve flap and the inlet valve seat are in sealed cooperation. A sensing cavity is formed between the inlet valve flap and the sensing cavity, and the sensing cavity is connected to the second cavity via a reflux channel. The inlet valve flap can be closed under the action of the inlet reset member and / or the fluid pressure in the sensing cavity to seal the inlet valve seat and isolate the first cavity from the water inlet, and can be opened under the action of the fluid pressure in the water inlet to connect the first cavity with the water inlet, thereby achieving sealed cooperation between the inlet valve flap and the inlet valve seat.

[0011] The outlet valve seat is arranged at the connecting channel;

[0012] The outlet valve flap is arranged in the second chamber and is connected to the inner wall of the shell through the outlet reset member so that the outlet valve flap and the outlet valve seat are sealed; the outlet valve flap can be closed under the action of the outlet reset member and / or the fluid pressure in the second chamber to seal the outlet valve seat and isolate the second chamber from the first chamber, and can be opened under the action of the fluid pressure in the first chamber to connect the second chamber with the first chamber.

[0013] Through the above conception, on the one hand, by using independent inlet valve flaps and outlet valve flaps, the problem of low reliability of the linked valve flap is avoided; on the other hand, by setting a backflow channel to connect the second chamber and the sensing chamber, when the fluid flows back and flows into the backflow preventer from the water outlet, the fluid enters the sensing chamber through the second chamber, and the inlet valve flap is closed by the combined action of the inlet reset member and the fluid pressure in the sensing chamber, thereby achieving the purpose of preventing the fluid from flowing back; at the same time, due to the introduction of fluid in the sensing chamber, the resistance characteristics of the inlet valve flap are changed, which can effectively reduce the water loss of the backflow preventer and improve the closing reliability of the backflow preventer; on the other hand, since there is no need to add additional auxiliary mechanisms, only a channel needs to be set inside the shell, and the backflow preventer has an optimized structure and is simple to assemble.

[0014] As a further preference, the shell includes an inlet shell and an outlet shell, and the inlet shell and the outlet shell are detachably connected; compared with the integral shell, the split shell is simpler to process, quicker to install, and easier to maintain.

[0015] As a further preference, the detachable connection between the inlet shell and the outlet shell is a bolt connection, which is convenient for assembly and disassembly.

[0016] As a further preference, the induction chamber is located inside the inlet shell, and the second chamber is located inside the outlet shell; the reflux channel is arranged inside the shell, and is formed by docking the first reflux channel located inside the inlet shell and the second reflux channel located inside the outlet shell; the first reflux channel and the second reflux channel are respectively processed on the inlet shell and the outlet shell, which is convenient to process.

[0017] As a further preference, a positioning pin is provided at the joint between the first return channel and the second return channel for connection and positioning of the inlet shell and the outlet shell.

[0018] As a further preference, the positioning pin is an elastic cylindrical pin.

[0019] As a further preferred embodiment, the backflow preventer also includes a test assembly; the test assembly includes a first test ball valve, a second test ball valve and a third test ball valve fixed to the shell; the first test ball valve, the second test ball valve and the third test ball valve each include a sensing end located inside the shell and a lead-out end located outside the shell, and the sensing ends of the first test ball valve, the second test ball valve and the third test ball valve are respectively connected to the water inlet, the first chamber and the sensing chamber; the test assembly is used to connect sensors to obtain fluid pressure, flow resistance, flow rate, etc. inside the backflow preventer; by connecting the first test ball valve, the second test ball valve and the third test ball valve to the water inlet, the first chamber and the sensing chamber respectively, the fluid pressures on both sides of the inlet valve disc and the outlet valve disc can also be obtained.

[0020] As a further preference, the first test ball valve, the second test ball valve and the third test ball valve are all fixed to the inlet housing, so that the function of the inlet housing is more integrated and the structure of the outlet housing is simpler.

[0021] As a further preference, the third test ball valve is connected to the first reflux channel to achieve connection with the sensing chamber; this connection method is not only simple to process, but also enables the third test ball valve to be connected to the sensing chamber and the second chamber at the same time; when the backflow preventer fluid flows in the reverse direction, the third test ball valve can be used to measure the fluid flowing back into the sensing chamber; when the backflow preventer fluid flows in the forward direction, the third test ball valve can also be used to measure the fluid flowing out of the backflow preventer from the second chamber, realizing dual use of one valve.

[0022] As a further preferred embodiment, one end of the inlet reset member is connected to the inlet valve disc, and the other end is connected to the bottom of the sensing cavity, so that the inlet valve disc is connected to the sensing cavity.

[0023] As a further preference, a positioning piece is connected to the inner wall of the shell, which is arranged between the outlet valve flap and the water outlet; one end of the outlet reset piece is connected to the outlet valve flap, and the other end is connected to the positioning piece, so that the outlet valve flap is connected to the inner wall of the shell.

[0024] As a further preference, the inlet reset member and the outlet reset member are both springs.

[0025] As a further preference, the outlet valve flap is also slidably connected to the positioning piece and to the outlet valve seat to form a double-guide structure, which limits the movement direction of the outlet valve flap, prevents the outlet valve flap from position deviation during movement, and ensures the sealing of the outlet valve flap.

[0026] As a further preference, the outlet valve flap is provided with a guide rod, and the positioning member and the outlet valve seat are both provided with guide elements. The guide rod passes through the guide elements of the positioning member and the outlet valve seat and moves back and forth to achieve a slidable connection between the outlet valve flap and the positioning member and the outlet valve seat.

[0027] As a further preference, the backflow preventer further comprises a leakage assembly, which is connected to the bottom of the shell, is connected to the first chamber, and is also in communication with the water inlet and the water outlet.

[0028] As a further preference, the drain assembly is connected below the inlet shell, so that the functions of the inlet shell are more integrated and the structure of the outlet shell is simpler.

[0029] In general, the above technical solutions conceived by the present invention have the following technical advantages compared with the existing technology:

[0030] 1. By using independent inlet valve flaps and outlet valve flaps, the problem of low reliability of linked valve flaps is avoided; by setting a backflow channel to connect the second chamber and the sensing chamber, when the fluid flows back, the fluid enters the sensing chamber through the second chamber, and the inlet valve flap is closed by the combined action of the inlet reset member and the fluid pressure in the sensing chamber, thereby preventing the fluid from flowing back; by introducing the fluid in the sensing chamber, the resistance characteristics of the inlet valve flap are changed, the water loss of the backflow preventer is effectively reduced, and the closing reliability of the backflow preventer is improved; by setting a channel inside the shell, there is no need to add additional auxiliary mechanisms, the backflow preventer has an optimized structure and simple assembly.

[0031] 2. By splitting the shell into an inlet shell and an outlet shell, and making the inlet shell and the outlet shell detachable, the shell processing is simple, the installation is quick, and the maintenance is convenient.

[0032] 3. By dividing the reflux channel into the first reflux channel and the second reflux channel and providing a positioning pin at the connection between the first reflux channel and the second reflux channel, processing is facilitated and the connection and positioning of the inlet shell and the outlet shell are facilitated.

[0033] 4. By setting up a test assembly and connecting the three ball valves of the test assembly to the water inlet, the first chamber and the sensing chamber respectively, the internal fluid parameters of the backflow preventer can be obtained, and the fluid pressure on both sides of the inlet valve disc and the outlet valve disc can be obtained; and the third test ball valve is connected to the sensing chamber by connecting to the first reflux channel, so that the third test ball valve can achieve dual purposes.

[0034] 5. By connecting both the test assembly and the drain assembly to the inlet housing, the inlet housing function is more integrated and the outlet housing structure is simpler. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 is a cross-sectional view of a backflow preventer according to an embodiment of the present invention;

[0036] Figure 2 is a schematic diagram of the backflow preventer according to an embodiment of the present invention when the fluid is flowing in the forward direction;

[0037] Figure 3 Schematic diagram of the backflow preventer according to an embodiment of the present invention when the fluid flows in the reverse direction.

[0038] Throughout the drawings, the same reference numerals are used to denote the same elements or structures, wherein:

[0039] Shell 1, water inlet 2, water outlet 3, inlet valve disc 4, outlet valve disc 5, inlet valve seat 6, outlet valve seat 7, test assembly 8, drain valve 9, positioning pin 10, inlet shell 11, outlet shell 12, sensing chamber 13, sensing chamber 14, first chamber 15, second chamber 16, connecting channel 17, return channel 18, positioning member 19, inlet reset member 41, inlet valve disc guide rod 42, outlet reset member 51, outlet valve disc guide rod 52, first test ball valve 81, second test ball valve 82, third test ball valve 83. DETAILED DESCRIPTION

[0040] In order to make the objectives, technical solutions, and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0041] like Figure 1 As shown, the backflow preventer provided by the embodiment of the present invention includes a housing 1, an inlet valve seat 6, an inlet valve flap 4, an outlet valve seat 7, an outlet valve flap 5, and a water inlet 2 and a water outlet 3 provided at both ends of the housing 1;

[0042] The inner cavity of the housing 1 is divided into a first chamber 15 and a second chamber 16; one side of the first chamber 15 is connected to the water inlet 2, and the other side is connected to the second chamber 16 through a connecting channel 17; a sensing cavity 13 is provided inside the first chamber 15, and the sensing cavity 13 is provided with an opening toward the water inlet 2; the second chamber 16 is connected to the water outlet 3 on the side away from the connecting channel 17;

[0043] The inlet valve seat 6 is arranged at the water inlet 2;

[0044] The inlet valve flap 4 is slidably and sealingly connected to the opening of the sensing chamber 13 and is connected to the sensing chamber 13 via the inlet reset member 41, so that the inlet valve flap 4 and the inlet valve seat 6 are sealed. A sensing chamber 14 is formed between the inlet valve flap 4 and the sensing chamber 13, and the sensing chamber 14 is connected to the second chamber 16 via the return channel 18. The inlet valve flap 4 can be closed under the action of the inlet reset member 41 and / or the fluid pressure in the sensing chamber 14 to seal the inlet valve seat 6 and isolate the first chamber 15 from the water inlet 2. It can also be opened under the action of the fluid pressure in the water inlet 2 to connect the first chamber 15 with the water inlet 2, thereby achieving a sealed cooperation between the inlet valve flap 4 and the inlet valve seat 6.

[0045] The outlet valve seat 7 is provided at the connecting passage 17;

[0046] The outlet valve flap 5 is arranged in the second chamber 16 and is connected to the inner wall of the shell 1 through the outlet reset member 51 so as to be sealed with the outlet valve seat 7; the outlet valve flap 5 can be closed under the action of the outlet reset member 51 and / or the fluid pressure in the second chamber 16 to seal the outlet valve seat 7, thereby isolating the second chamber 16 from the first chamber 15, and can be opened under the action of the fluid pressure in the first chamber 15 to connect the second chamber 16 with the first chamber 15.

[0047] Through the mutual cooperation of the above-mentioned components, when the fluid flows forward, the inlet valve flap 4 and the outlet valve flap 5 are opened, and the fluid passes through the backflow preventer, and the fluid pressure loss is small in this process; when backflow occurs, the outlet valve flap 5 and the inlet valve flap 4 are closed to prevent the fluid from flowing out of the backflow preventer, and the closing reliability of the outlet valve flap 5 and the inlet valve flap 4 is high, which is practical and advanced.

[0048] Each component will be described in more detail below.

[0049] In the embodiment of the present invention, Figure 1 As shown in the figure, the shell 1 includes an inlet shell 11 and an outlet shell 12, and the inlet shell 11 and the outlet shell 12 are detachably connected. In this embodiment, the inlet shell 11 and the outlet shell 12 are detachably connected by bolts. Compared with the integral shell, the split shell is simple to process, quicker to install, simple to disassemble and easy to maintain.

[0050] In the embodiment of the present invention, Figure 1 As shown in the figure, the induction chamber 14 is located inside the inlet shell 11, the second chamber 16 is located inside the outlet shell 12, and the first chamber 15 is formed by splicing the inlet shell 11 and the outlet shell 12; in this embodiment, the return channel 18 is arranged inside the shell 1, and is formed by docking the first return channel located inside the inlet shell 11 and the second return channel located inside the outlet shell 12; the first return channel and the second return channel are processed on the inlet shell 11 and the outlet shell 12 respectively, which is convenient to process; a positioning pin 10 is provided at the docking point of the first return channel and the second return channel for connection and positioning of the inlet shell 11 and the outlet shell 12; in this embodiment, the positioning pin 10 is an elastic cylindrical pin.

[0051] In the embodiment of the present invention, Figure 1As shown in the figure, one end of the inlet reset member 41 is connected to the inlet valve disc 4, and the other end is connected to the bottom of the sensing cavity 13, so that the inlet valve disc 4 is connected to the sensing cavity 13; in this embodiment, the inlet reset member 41 is an inlet spring; in this embodiment, protrusions are provided at the bottom of the sensing cavity 13 and on the side of the inlet valve disc 4 facing the bottom of the sensing cavity 13, and the two ends of the inlet spring are respectively sleeved on the outer side of the protrusions on the bottom of the sensing cavity 13 and the inlet valve disc 4 to achieve connection with the bottom of the sensing cavity 13 and the inlet valve disc 4; in some embodiments, the inlet reset member 41 can also be a telescopic rod.

[0052] In the embodiment of the present invention, Figure 1 As shown in the figure, the inlet valve flap 4 is provided with an inlet valve flap guide rod 42 facing the inlet valve seat 6. The inlet valve flap guide rod 42 is slidably connected to the inlet valve seat 6. Through the slidable connection between the inlet valve flap guide rod 42 and the inlet valve seat 6, and the slidable sealing connection between the inlet valve flap 4 and the sensing cavity 13, a unidirectional double-guide structure is formed, which limits the movement direction of the inlet valve flap 4, ensures the sealing of the inlet valve flap 4, and prevents the inlet valve flap 4 from position deviation during movement.

[0053] In the embodiment of the present invention, Figure 1 As shown in the figure, a positioning member 19 is connected to the inner wall of the shell 1, and the positioning member 19 is arranged between the outlet valve flap 5 and the water outlet 3; one end of the outlet reset member 51 is connected to the outlet valve flap 5, and the other end is connected to the positioning member 19, so that the outlet valve flap 5 is connected to the inner wall of the shell 1; specifically, in this embodiment, the positioning member 19 is arranged at the water outlet 3; in some embodiments, the positioning member 19 can also be arranged inside the second chamber 16; in this embodiment, the outlet reset member 51 is a spring; in some embodiments, the outlet reset member 51 can also be a telescopic rod.

[0054] In the embodiment of the present invention, Figure 1 As shown in the figure, the outlet valve flap 5 is provided with an outlet valve flap guide rod 52, which is slidably connected to the positioning member 19 and the outlet valve seat 7 to form a unidirectional double-guide structure, which limits the movement direction of the outlet valve flap 5, ensures the sealing of the outlet valve flap 5, and prevents the outlet valve flap 5 from having position deviation during movement; specifically, the positioning member 19 and the outlet valve seat 7 are both provided with guide elements, and the outlet valve flap guide rod 52 passes through the guide elements of the positioning member 19 and the outlet valve seat 7 and moves back and forth to realize the slidable connection between the outlet valve flap 5 and the positioning member 19 and the outlet valve seat 7.

[0055] In the embodiment of the present invention, Figure 1As shown in , the backflow preventer also includes a test assembly 8; the test assembly 8 includes a first test ball valve 81, a second test ball valve 82 and a third test ball valve 83 fixed to the shell 1; the first test ball valve 81, the second test ball valve 82 and the third test ball valve 83 each include a sensing end located inside the shell 1 and a lead-out end located outside the shell 1, and the sensing ends of the first test ball valve 81, the second test ball valve 82 and the third test ball valve 83 are respectively connected to the water inlet 2, the first chamber 15 and the sensing chamber 14; the test assembly 8 is used to connect a sensor to obtain the fluid pressure, flow resistance, flow rate, etc. inside the backflow preventer; the first test ball valve 81, the second test ball valve 82 and the third test ball valve 83 are respectively connected to the water inlet 2, the first chamber 15 and the sensing chamber 14, and the inlet valve disc 4 and the outlet valve disc 4 can also be obtained. The fluid pressures borne by both sides of the valve disc 5 respectively; in this embodiment, the first test ball valve 81, the second test ball valve 82 and the third test ball valve 83 are all fixed to the inlet shell 11; the function of the inlet shell 11 is more integrated and the structure of the outlet shell 12 is simpler; in this embodiment, the third test ball valve 83 is connected to the first reflux channel to achieve connection with the sensing chamber 14; this connection method is not only simple to process, but also enables the third test ball valve 83 to be connected to the sensing chamber 14 and the second chamber 16 at the same time. When the backflow preventer fluid flows in reverse, the third test ball valve 83 can be used to measure the fluid flowing back into the sensing chamber 14; when the backflow preventer fluid flows forward, the third test ball valve 83 can also be used to measure the fluid flowing out of the backflow preventer from the second chamber 16, realizing dual use of one valve.

[0056] In the embodiment of the present invention, Figure 1 As shown in the figure, the backflow preventer also includes a leakage component, which is connected to the bottom of the shell 1 and is connected to the first chamber 15, and is also connected to the water inlet 2 and the water outlet 3; in this embodiment, the leakage component is a leakage valve 9, which is connected to the bottom of the inlet shell 11 and is connected to the water inlet 2 and the water outlet 3 through pipes.

[0057] The above examples are used to illustrate the backflow preventer of the present invention and do not limit the scope of protection of the present invention.

[0058] The following combination Figure 2 and Figure 3 , the working process of the backflow preventer of the present invention is further described in detail.

[0059] like Figure 2 As shown in , when the fluid flows forward, the fluid enters the water inlet 2, pushes open the inlet valve disc 4, and flows into the first chamber 15. The fluid then pushes open the outlet valve disc 5, flows into the second chamber 16, and flows out through the water outlet 3.

[0060] like Figure 3As shown in , when the fluid flows in the reverse direction, the fluid flows into the water outlet 3, enters the second chamber 16 and closes the outlet valve flap 5 to prevent the fluid from flowing back into the first chamber 15; at the same time, the fluid flows from the second chamber 16 into the sensing chamber 14 through the reflux channel 18, thereby increasing the fluid pressure in the sensing chamber 14; the inlet valve flap 4 is closed under the combined action of the inlet spring force and the fluid pressure in the sensing chamber 14 to seal the water inlet 2 and further prevent the fluid from flowing back; at this time, the discharge valve 9 is opened, and the residual fluid in the first chamber 15 flows out from the discharge valve 9, while the first chamber 15 is connected to the atmosphere, and the outlet valve flap 5 is further closed under the action of the fluid pressure flowing back into the second chamber 16.

[0061] In this embodiment, since a reflux channel 18 is provided to connect the second chamber 16 with the sensing chamber 14, when backflow occurs, the fluid enters the sensing chamber 14 from the second chamber 16, so that the fluid pressure in the sensing chamber 14 increases, and the inlet valve flap 4 is closed under the combined action of the inlet spring force and the fluid pressure; due to the participation of the fluid pressure, the reliability of the closing of the inlet valve flap 4 is improved, and a smaller inlet spring can be used while meeting the anti-backflow reliability; due to the reduction in the inlet spring specification, the resistance encountered during the forward flow of the fluid is reduced, thereby reducing the pressure loss of the fluid, and therefore, the water loss of the backflow preventer is reduced; in some embodiments, when the inlet reset member 41 is a telescopic rod, a smaller telescopic rod can be used while meeting the anti-backflow reliability. It can be understood that the purpose of reducing the water loss of the backflow preventer can also be achieved.

[0062] At the same time, in this embodiment, due to the use of independent inlet valve flap 4 and outlet valve flap 5, the problem of low reliability of linked valve flap is avoided; since only a channel is set inside the shell 1 without the need for additional auxiliary mechanisms, the backflow preventer has an optimized structure and is easy to assemble.

[0063] In summary, the backflow preventer according to the present invention has high reliability, small water loss and simple processing and assembly, and is therefore particularly suitable for applications in preventing backflow pollution in pipelines.

[0064] It will be easily understood by those skilled in the art that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A backflow preventer, characterized in that: It comprises a housing (1), an inlet valve seat (6), an inlet valve flap (4), an outlet valve seat (7), an outlet valve flap (5), and a water inlet (2) and a water outlet (3) arranged at both ends of the housing (1); The inner cavity of the shell (1) is divided into a first chamber (15) and a second chamber (16); one side of the first chamber (15) is connected to the water inlet (2), and the other side is connected to the second chamber (16) via a connecting channel (17); a sensing chamber (13) is provided inside the first chamber (15), and the sensing chamber (13) is provided with an opening toward the water inlet (2); the second chamber (16) is connected to the water outlet (3) on a side away from the connecting channel (17); The inlet valve seat (6) is arranged at the water inlet (2); The inlet valve flap (4) is slidably and sealingly connected to the opening of the sensing cavity (13), and is connected to the sensing cavity (13) via an inlet reset member (41), so that the inlet valve flap (4) and the inlet valve seat (6) are in sealing cooperation; a sensing cavity (14) is formed between the inlet valve flap (4) and the sensing cavity (13), and the sensing cavity (14) is communicated with the second chamber (16) via a return channel (18); The outlet valve seat (7) is arranged at the connecting channel (17); The outlet valve flap (5) is arranged in the second chamber (16) and is connected to the inner wall of the housing (1) via an outlet reset member (51) so that the outlet valve flap (5) is in sealing cooperation with the outlet valve seat (7); The housing (1) comprises an inlet housing (11) and an outlet housing (12), wherein the inlet housing (11) and the outlet housing (12) are detachably connected; The sensing chamber (14) is located inside the inlet housing (11), and the second chamber (16) is located inside the outlet housing (12); the return channel (18) is provided inside the housing (1), and is formed by the connection of a first return channel located inside the inlet housing (11) and a second return channel located inside the outlet housing (12); A positioning pin (10) is provided at the joint between the first reflux channel and the second reflux channel; The backflow preventer further comprises a leakage assembly, which is connected to the bottom of the housing (1), is connected to the first chamber (15), and is also in communication with the water inlet (2) and the water outlet (3); The backflow preventer further comprises a test assembly (8); the test assembly (8) comprises a first test ball valve (81), a second test ball valve (82) and a third test ball valve (83) fixed to the housing (1); the first test ball valve (81), the second test ball valve (82) and the third test ball valve (83) each comprise a sensing end located inside the housing (1) and a lead end located outside the housing (1), and the sensing ends of the first test ball valve (81), the second test ball valve (82) and the third test ball valve (83) are respectively connected to the water inlet (2), the first chamber (15) and the sensing chamber (14); The first test ball valve (81), the second test ball valve (82), and the third test ball valve (83) are all fixed to the inlet housing (11); the third test ball valve (83) is connected to the first reflux channel to achieve connection with the sensing chamber (14); The third test ball valve (83) is connected to the sensing chamber (14) and the second chamber (16) at the same time. When the backflow preventer fluid flows in the reverse direction, the third test ball valve (83) can be used to measure the fluid flowing back into the sensing chamber (14); when the backflow preventer fluid flows in the forward direction, the third test ball valve (83) can also be used to measure the fluid flowing out of the backflow preventer from the second chamber (16). The inlet reset member (41) and the outlet reset member (51) are both springs.

2. The backflow preventer according to claim 1, wherein: One end of the inlet resetting member (41) is connected to the inlet valve flap (4), and the other end is connected to the bottom of the sensing cavity (13), so that the inlet valve flap (4) is connected to the sensing cavity (13).

3. The backflow preventer according to claim 1, wherein: The inner wall of the housing (1) is connected to a positioning member (19), which is arranged between the outlet valve flap (5) and the water outlet (3); one end of the outlet resetting member (51) is connected to the outlet valve flap (5), and the other end is connected to the positioning member (19), so that the outlet valve flap (5) is connected to the inner wall of the housing (1).

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