CN210423831U - Low-resistance backflow preventer - Google Patents

Abstract

The utility model provides a low resistance backflow preventer belongs to valve manufacturing technical field. It has solved the current low resistance backflow preventer bulky, with high costs scheduling problem. This low resistance backflow preventer includes the valve body, inlet check valve and export check valve, the valve body has the water inlet, lumen and delivery port, the valve body top is connected with the valve gap, inlet check valve and export check valve structure are unanimous and both are all the level set up in the valve body, be equipped with in the valve body and lie in between inlet check valve and the export check valve and make inlet check valve communicate in the water spare that crosses of export check valve, it has the intercommunication structure that communicates in the lumen to cross the water spare, the valve body lower part has rather than linking an organic whole and be used for the drainage structures of drainage. The utility model has the advantages of compact structure, good working stability, convenient maintenance and the like.

Description

Low-resistance backflow preventer

Technical Field

The utility model belongs to the technical field of the valve is made, a low resistance backflow preventer is related to.

Background

The low resistance backflow preventer is another new type of valve device for preventing backflow of liquid after the advent of the common check valve. The water power control combination device which can strictly limit the unidirectional flow of water in the pipeline is developed under the condition that the backflow pollution of the domestic drinking water pipeline is serious but no device for effectively preventing backflow pollution is provided according to the urban and rural water supply pipe network on the current world, and the backflow preventer is low in energy consumption and safe. The safety water drain valve is mainly characterized in that the backflow of water in a pipe network is thoroughly prevented under any working condition, even if the second check valve is damaged, the safety water drain valve can be immediately opened automatically, and the backflow water is drained out of a pipeline system, so that backflow pollution is thoroughly prevented, and the sanitation and safety of drinking water of people are guaranteed. At present, the low-resistance backflow preventer is mainly used for effectively separating water quality systems such as municipal water supply networks and user pipe networks or domestic water, fire water, air-conditioning water, greening water and the like, and therefore the backflow preventer is also commonly called an antifouling isolating valve.

For example, chinese patent literature discloses a hydraulic low resistance backflow preventer [ application No.: 201520231786.8, respectively; authorization notice number: CN204553950U ], which comprises three parts of a detection valve, a main valve and a drainer, wherein the detection valve and the drainer are respectively connected with the whole of the main valve into a whole, the detection valve is arranged on the upper edge of the main valve, the drainer is arranged on the lower edge of the main valve, the main valve comprises a valve cover, a valve body, an inlet device, an outlet device, an inlet, a middle cavity and an outlet, the inlet device comprises an inlet spring, a piston, an inlet shaft, an inlet valve clack and an inlet valve seat which are arranged on the same central line, a balance hole is arranged on the right side of the valve cover, the bottom of the inlet valve seat is connected with the valve body, a filter screen is arranged on the inlet valve seat, the inlet end of the inlet is provided with a telescopic ring, the inlet device is communicated with the inlet, the outlet device comprises an outlet spring, an outlet shaft, an outlet valve clack and an, and is designed into a full-bore valve cavity flow passage and is arranged at the upper part of the left side of the main valve.

Foretell low resistance backflow preventer of water conservancy type can reduce the spring strength and the water loss of import check valve, and the valve gap can be opened, is convenient for detect, maintain and maintain, but is the valve body of Y type valve chamber structure and will connect the drainer outward for whole bulky, the installation of being not convenient for, import device and outlet device structure are not unified moreover, have increased manufacturing cost.

Disclosure of Invention

The utility model aims at providing a compact structure, job stabilization nature is good, convenient to overhaul's low resistance backflow preventer to the above-mentioned problem that exists among the prior art.

The purpose of the utility model can be realized by the following technical proposal: the utility model provides a low resistance backflow preventer, includes valve body, inlet check valve and outlet check valve, the valve body water inlet, lumen and delivery port have, inlet check valve be located water inlet department in order to avoid the water backflow of lumen to the water inlet, outlet check valve be located the water backflow of delivery port department in order to avoid the delivery port to the lumen, a serial communication port, the valve body top be connected with the valve gap, inlet check valve and outlet check valve structure unanimous and both average levels set up in the valve body, the valve body in be equipped with and be located between inlet check valve and the outlet check valve and make inlet check valve communicate in outlet check valve's water spare of crossing, the water spare of crossing have the intercommunication structure who communicates in the lumen, the valve body lower part have rather than linking into an organic whole and be used for the drainage structures.

The low-resistance backflow preventer integrates the drainage structure at the lower part of the valve body, so that the structure is compact; the valve cover on the top of the valve body is opened, so that internal parts can be detected, and the detection is convenient; the inlet check valve and the outlet check valve have the same structure, so that the cost is low and the assembly is convenient; in the use, when export water pressure was too high and was makeed the infiltration of export check valve, the water under high pressure of export not only got into the lumen from the connectivity structure who crosses the water spare, and later the water under high pressure passes through drainage structures and discharges, and the drainage is smooth and easy, and the water under high pressure flows and acts on the import check valve from crossing the water spare moreover, has strengthened the sealed non return effect of import check valve, has improved the sealed sensitivity of import check valve non return, has guaranteed the job stabilization nature of import check valve, and is high to the utilization ratio of export water under high pressure, reduces.

In foretell low resistance backflow preventer, the water passing part have and be the tube-shape portion that is the tube-shape and lies in between inlet check valve and the outlet check valve, the both sides portion of tube-shape portion be the binding face of laminating in the perpendicular inner wall of valve body, the top of tube-shape portion have and be the extension portion that tile form axial extension and cladding are in inlet check valve top department. Therefore, the two sides and the top of the water passing piece are positioned, the water passing piece is firmly connected, the water flow impact resistance is good, and the work is stable.

In the low resistance backflow preventer, the communicating structure comprises a water passing opening which is arranged at the bottom of the cylindrical part, axially extends and radially penetrates through the water passing opening. The high pressure water at the outlet seeps out of the outlet check valve and flows through the water piece, and then flows to the middle cavity from the water outlet.

In the low resistance backflow preventer, the inner wall of the cylindrical part is a conical surface, and the end part with a large diameter is positioned on the inlet check valve side. The cone plays the guide expansion effect to the water under high pressure that oozes from the outlet check valve, and is high to water under high pressure utilization ratio for the inlet check valve atress is even, keeps the sealed effectual of non return.

In foretell low resistance backflow preventer, drainage structures include that the valve body lower part has rather than the drain valve body that fuses, the drain valve body link firmly the drainage valve gap and the centre gripping has the diaphragm between drain valve body and the drain valve lid, diaphragm and drain valve lid between form first cavity, for the second cavity that is linked together with the lumen between diaphragm and the exhaust valve body, the drain valve body still have the drainage cavity that passes through the drainage channel intercommunication with the second cavity, the diaphragm on be connected with the drainage case, the internal drainage spring and the drainage spring that are equipped with of drain valve provide elasticity and make the drainage case have the trend of keeping away from drainage channel all the time, the valve body in have the inlet channel who communicates in the water inlet, the drain valve lid have the connecting channel that makes inlet channel and first cavity be linked together.

In the low-resistance backflow preventer, a sealing ring positioned at the periphery of the connecting channel is embedded between the drain valve cover and the valve body. Thus, the tightness between the connecting channel and the water inlet channel is ensured, and water leakage is avoided.

In foretell low resistance backflow preventer, the drainage case including be located the first case in first chamber and be located the second case in the second chamber, the diaphragm centre gripping between first case and second case, the drain valve lid guiding hole has, first case insert in the guiding hole and first case inlay and be equipped with the O type circle sealed in the guiding hole inner wall, drainage channel inlay and be equipped with the disk seat that is the tube-shape, the disk seat inner wall convex circle has, the disk seat outer wall that supplies second valve core male guide part and guide part have the radial through-hole that link up of a plurality of, the tip of second case inlay and be equipped with sealed the pad, the drainage spring housing outside the guide part and provide elasticity and make the second valve core have the trend of keeping away from the disk seat. Drainage spring's one end is contradicted in the drain valve body, and the drainage spring other end is contradicted in the second case, and the guiding hole makes first case axial displacement steady, and the guiding part makes second case axial displacement steady, and the through-hole supplies the lumen water to pass through, and the drainage is smooth and easy.

In foretell low resistance backflow preventer, inlet check valve and outlet check valve all include non return disk seat, non return casing, non return case and non return spring, non return disk seat outer wall inlay and be equipped with the sealing ring, the non return casing include guide cylinder, connecting rib, non return case pass the guide cylinder setting, connecting rib circumference equipartition in the guide cylinder setting and make guide cylinder and non return casing link firmly mutually, non return casing the opening that has the circumference equipartition, non return spring housing outside the guide part and provide elasticity and make non return case have the trend sealed in the non return disk seat all the time, non return case towards the tip of non return disk seat inlay and be equipped with the rubber pad and this end connection has the screw, screw and rubber pad between be equipped with the compression gasket.

In foretell low resistance backflow preventer, the valve body on be connected with the water inlet ball valve that is linked together with the water inlet, the valve gap on be connected with the valve gap ball valve that is linked together with the lumen, the valve body on still be connected with the delivery port ball valve that is linked together with the delivery port.

In the low-resistance backflow preventer, the water inlet and the water outlet are both connected with an on-off valve for controlling on-off.

Compared with the prior art, this low resistance backflow preventer reasonable in design, with drainage structures integration in the valve body lower part, the connecting pipe has been saved, the joint is arranged, make compact structure, the equipment is convenient, whole small, and open the valve gap at valve body top, can detect internals, it is convenient to detect, import check valve and outlet check valve structure are unanimous, make with low costs, the assembly of also being convenient for, the sealed non return effect of import check valve has been strengthened in setting up of water spare, the sealed sensitivity of import check valve non return has been improved, high to the utilization ratio of outlet high pressure water, reduce the water loss, job stabilization nature is good.

Drawings

FIG. 1 is a sectional view showing the structure of the low resistance backflow preventer.

FIG. 2 is an exploded view of the low resistance backflow preventer.

Fig. 3 is an enlarged view of the structure of fig. 1 at circle a.

In the figure, 1, a valve body; 2. an inlet check valve; 3. an outlet check valve; 4. a water inlet; 5. a middle cavity; 6. a water outlet; 7. a valve cover; 8. a water passing part; 81. a cylindrical portion; 82. a binding face; 83. an extension part; 84. a water outlet; 9. a drain valve body; 10. a drain valve cover; 11. a membrane; 12. a first chamber; 13. a second chamber; 14. a drainage chamber; 15. a drain valve core; 16. a drainage spring; 17. a water inlet channel; 18. a connecting channel; 19. a seal ring; 20. a first valve spool; 21. a second valve core; 22. an O-shaped ring; 23. a valve seat; 24. a convex ring; 25. a guide portion; 26. a through hole; 27. a gasket; 28. a check valve seat; 29. a non-return housing; 291. a guide cylinder; 292. a connecting rib; 293. a flow-through hole; 30. a check valve core; 31. a check spring; 32. a seal ring; 33. a rubber pad; 34. a screw; 35. compressing the gasket; 36. a water inlet ball valve; 37. a bonnet ball valve; 38. a water outlet ball valve; 39. and opening and closing the valve.

Detailed Description

The following are specific embodiments of the present invention and the accompanying drawings are used to further describe the technical solution of the present invention, but the present invention is not limited to these embodiments.

As shown in fig. 1, fig. 2 and fig. 3, this low resistance backflow preventer includes valve body 1, inlet check valve 2 and outlet check valve 3, valve body 1 has water inlet 4, lumen 5 and delivery port 6, inlet check valve 2 is located water backflow to water inlet 4 in order to avoid lumen 5 in the water inlet 4, outlet check valve 3 is located delivery port 6 so as to avoid delivery port 6's water backflow to lumen 5, valve body 1 top is connected with valve gap 7, inlet check valve 2 is unanimous with outlet check valve 3 structure and both are all horizontally set up in valve body 1, be equipped with in valve body 1 and be located between inlet check valve 2 and the outlet check valve 3 and make inlet check valve 2 communicate in outlet check valve 3's water spare 8 of crossing, it has the intercommunication structure that communicates in lumen 5 to cross water spare 8, valve body 1 lower part has rather than the drainage structures that fuses and be used for the drainage.

The low-resistance backflow preventer integrates the drainage structure at the lower part of the valve body 1, so that the structure is compact; the valve cover 7 at the top of the valve body 1 is opened, so that internal parts can be detected, and the detection is convenient; the inlet check valve 2 and the outlet check valve 3 are consistent in structure, so that the cost is low and the assembly is convenient; in the use, when the water pressure of delivery port 6 was too high to make 3 water seepage of outlet check valve, the water under high pressure of delivery port 6 got into lumen 5 from the communicating structure who crosses water spare 8, later the water under high pressure passes through drainage structures and discharges, the drainage is smooth and easy, flow through and act on inlet check valve 2 from crossing water spare 8 in addition, inlet check valve 2's sealed non return effect has been strengthened, the sealed sensitivity of inlet check valve 2 non return has been improved, inlet check valve 2's job stabilization nature has been guaranteed, high to the utilization ratio of the 6 water under high pressure of delivery port, reduce the water loss.

More specifically, the water passing member 8 has a cylindrical portion 81 which is cylindrical and located between the inlet check valve 2 and the outlet check valve 3, both side portions of the cylindrical portion 81 are bonding surfaces 82 which are bonded to the vertical inner wall of the valve body 1, the top portion of the cylindrical portion 81 has an extension portion 83 which is tile-shaped and axially extends and covers the top portion of the inlet check valve 2, the communicating structure includes an axially extending and radially penetrating water passing port 84 which is formed in the bottom portion of the cylindrical portion 81, and the inner wall of the cylindrical portion 81 is a conical surface and the end portion with the large diameter is located on the inlet check valve 2 side.

Drainage structure includes that what valve body 1 lower part had rather than the drain valve body 9 of uniting into an organic whole, drain valve body 9 links firmly drain valve lid 10 and the centre gripping has diaphragm 11 between drain valve body 9 and the drain valve lid 10, form first cavity 12 between diaphragm 11 and the drain valve lid 10, be the second cavity 13 that is linked together with lumen 5 between diaphragm 11 and the exhaust valve body 1, drain valve body 9 still has the drainage cavity 14 that communicates through drainage channel with second cavity 13, be connected with drainage case 15 on the diaphragm 11, be equipped with drainage spring 16 in the drain valve body 9 and drainage spring 16 provide elasticity and make drainage case 15 have the trend of keeping away from drainage channel all the time, it communicates in the water inlet channel 17 of water inlet 4 to have in valve body 1, drain valve lid 10 has the interface channel 18 that makes water inlet channel 17 and first cavity 12 be linked together, it is equipped with the sealing washer 19 that is located interface channel 18 periphery to inlay between drain valve lid 10 and the valve body 1.

The drain valve core 15 comprises a first valve core 20 positioned in the first chamber 12 and a second valve core 21 positioned in the second chamber 13, the diaphragm 11 is clamped between the first valve core 20 and the second valve core 21, the drain valve cover 10 is provided with a guide hole, the first valve core 20 is inserted into the guide hole, an O-shaped ring 22 sealed on the inner wall of the guide hole is embedded in the first valve core 20, a cylindrical valve seat 23 is embedded in the drain channel, the inner wall of the valve seat 23 is provided with a convex ring 24, the valve seat 23 is provided with a guide part 25 for inserting the second valve core 21, the outer wall of the guide part 25 is provided with a plurality of through holes 26 which are radially communicated, a sealing gasket 27 is embedded in the end part of the second valve core 21, and the drain spring 16 is sleeved outside the guide part 25 and provides elastic force so that the second valve core 21 has a tendency of being.

Inlet check valve 2 and outlet check valve 3 all include check valve seat 28, non return casing 29, non return case 30 and check spring 31, non return valve seat 28 outer wall inlays and is equipped with sealing ring 32, non return casing 29 includes guide cylinder 291, connecting rib 292, non return case 30 passes guide cylinder 291 and sets up, connecting rib 292 circumference equipartition is in guide cylinder 291 setting and makes guide cylinder 291 and non return casing 29 link firmly mutually, non return casing 29 has the circulation hole 293 of circumference equipartition, non return spring 31 overlaps outside guide part 25 and provides elasticity and makes non return case 30 have the trend sealed in non return valve seat 28 all the time, non return case 30 inlays towards the tip of non return valve seat 28 and is equipped with rubber pad 33 and this end connection has screw 34, be equipped with between screw 34 and the rubber pad 33 and compress tightly gasket 35. The check valve seat 28 of the inlet check valve 2 is inserted into the water inlet 4, the check shell 29 of the inlet check valve 2 is partially inserted into the water inlet 4, the sealing ring 32 of the inlet check valve 2 is sealed on the inner wall of the water inlet 4 to ensure the sealing performance, the check valve shaft and the check shell 29 of the outlet check valve 3 are inserted into the water outlet 6, and the sealing ring 32 of the outlet check valve 3 is sealed on the inner wall of the water outlet 6 to ensure the sealing performance.

The water inlet ball valve 36 communicated with the water inlet 4 is connected to the valve body 1, the valve cover ball valve 37 communicated with the middle cavity 5 is connected to the valve cover 7, the water outlet ball valve 38 communicated with the water outlet 6 is further connected to the valve body 1, the water inlet ball valve 36, the valve cover ball valve 37 and the water outlet ball valve 38 are convenient for a pressure gauge to be connected, then the ball valves are opened, the water pressure of the water inlet 4, the middle cavity 5 and the water outlet 6 can be observed, the regulation and control and the quality inspection are convenient, and the water head loss condition is. The water inlet 4 and the water outlet 6 are both connected with an on-off valve 39 for controlling on-off, the on-off valve 39 is used for closing or opening a water flow channel so as to be convenient for maintenance, the on-off valve 39 can be a gate valve, a ball valve or a stop valve, and the on-off valve 39 is a ball valve in the embodiment.

The working principle of the low-resistance backflow preventer is as follows: when the pressure of the pipe network is normal, water can easily enter from the water inlet 4, pass through the inlet check valve 2 and the outlet check valve 3 and then flow out from the water outlet 6. Because the water pressure in the middle cavity 5 is lower than the water pressure at the water inlet 4 due to the local resistance of the inlet check valve 2, the water in the water inlet 4 flows into the first cavity 12 through the water inlet channel 17 and the connecting channel 18, the water pressure of the first cavity 12 is consistent with the water pressure of the water inlet 4, the water pressure of the second cavity 13 is consistent with the water pressure of the middle cavity 5, the water pressure of the first cavity 12 is higher than the water pressure of the second cavity 13, the elasticity of the drainage spring 16 is overcome, the drainage valve core 15 seals the drainage channel, the drainage cavity 14 cannot drain water, and the water in the pipe network normally flows. When the valve behind the water outlet 6 of the low-resistance backflow preventer is closed, water flow keeps a static state, the water pressure at the water inlet 4 is unchanged, the water pressure in the first chamber 12 is still higher than that in the second chamber 13, and the drainage valve core 15 still achieves a sealing state.

When the water pressure of the pipeline behind the water outlet 6 of the low-resistance backflow preventer rises and exceeds the water pressure of the water inlet 4, if the outlet check valve 3 does not leak, high-pressure water cannot flow back into the middle cavity 5, and the water pressure in the middle cavity 5 still keeps normal flow, so the drainage valve core 15 still plays a closing role and cannot drain water; if the outlet check valve 3 leaks, the water pressure in the middle cavity 5 is increased due to the leakage, that is, the water pressure in the second cavity 13 is increased, and the water discharge valve core 15 is far away from the water discharge channel due to the elastic action of the water discharge spring 16, so that the water in the second cavity 13 flows out from the water discharge cavity 14, the inlet check valve 2 still keeps a sealing state, and the high-pressure water is prevented from flowing back to the pipeline at the front section of the water inlet 4 to cause backflow pollution.

When the water pressure of the water inlet 4 is continuously reduced, the water pressure in the first chamber 12 is also continuously reduced, when the water pressure of the water inlet 4 is reduced to 0.02MPa, the difference between the water pressures at the two sides of the diaphragm 11 is not enough to keep the drainage spring 16 in a compressed state, and the elastic force of the drainage spring 16 drives the diaphragm 11 and the drainage valve core 15 to move towards the first chamber 12, so that the second chamber 13 is communicated with the drainage chamber 14 for drainage, and the inlet check valve 2 is prevented from leaking and flowing backwards; when the water pressure of the water inlet 4 is reduced to zero or negative pressure, the drainage valve core 15 is opened maximally, and air enters the second chamber 13 and the middle cavity 5 from the drainage chamber 14, so that an air interval is formed between the second chamber 13 and the middle cavity 5, the siphon backflow phenomenon is avoided, and the water in the pipeline stops flowing.

If the inlet check valve 2 leaks, the pressure difference between the first chamber 12 and the second chamber 13 cannot push the diaphragm 11 to overcome the elastic force of the drain spring 16, and the drain spool 15 opens, so that the drain chamber 14 continuously and intermittently drains water; since the high pressure water of the outlet check valve 3 has been depressurized, it will not flow back to the inlet check valve 2, although if the conditions allow, it is recommended that this low resistance backflow preventer should be overhauled in time.

Those not described in detail in this specification are within the skill of the art. The specific embodiments described herein are merely illustrative of the spirit of the invention. Various modifications, additions and substitutions for the specific embodiments described herein may be made by those skilled in the art without departing from the spirit of the invention or exceeding the scope of the invention as defined in the accompanying claims.

Claims (10)

1. The utility model provides a low resistance backflow preventer, includes valve body (1), inlet check valve (2) and outlet check valve (3), valve body (1) water inlet (4), lumen (5) and delivery port (6) have, inlet check valve (2) be located water inlet (4) and with the water reflux to water inlet (4) in avoiding lumen (5), outlet check valve (3) be located delivery port (6) and with the water reflux to lumen (5) of avoiding delivery port (6), its characterized in that, valve body (1) top be connected with valve gap (7), inlet check valve (2) and outlet check valve (3) structure unanimous and both are the level and set up in valve body (1), valve body (1) in be equipped with and be located between inlet check valve (2) and outlet check valve (3) and make inlet check valve (2) communicate in outlet check valve (3) cross water piece (8), the water passing piece (8) is provided with a communication structure communicated with the middle cavity (5), and the lower part of the valve body (1) is provided with a drainage structure which is connected with the valve body into a whole and is used for draining water.

2. A backflow preventer with low resistance according to claim 1, wherein the water passage member (8) has a cylindrical portion (81) which is cylindrical and located between the inlet check valve (2) and the outlet check valve (3), both side portions of the cylindrical portion (81) are abutting surfaces (82) which abut against the vertical inner wall of the valve body (1), and the top portion of the cylindrical portion (81) has an extension portion (83) which is in the form of a tile and extends axially and covers the top portion of the inlet check valve (2).

3. A low resistance backflow preventer according to claim 2, wherein the communicating structure comprises a water passing port (84) which is axially extended and radially penetrated and is provided at the bottom of the cylindrical part (81).

4. A low resistance backflow preventer according to claim 3, characterized in that the inner wall of the cylindrical part (81) is a tapered surface and the end part with a large diameter is located on the inlet check valve (2) side.

5. The low resistance backflow preventer according to claim 1 or 2 or 3 or 4, wherein the drain structure comprises a drain valve body (9) integrally connected with the lower portion of the valve body (1), the drain valve body (9) is fixedly connected with a drain valve cover (10), a diaphragm (11) is clamped between the drain valve body (9) and the drain valve cover (10), a first chamber (12) is formed between the diaphragm (11) and the drain valve cover (10), a second chamber (13) communicated with the middle chamber (5) is formed between the diaphragm (11) and the drain valve body (1), the drain valve body (9) further comprises a drain chamber (14) communicated with the second chamber (13) through a drain channel, the diaphragm (11) is connected with a drain valve core (15), a drain spring (16) is arranged in the drain valve body (9) and the drain spring (16) provides elasticity so that the drain valve core (15) always tends to be far away from the drain channel, the valve body (1) in have and communicate in inhalant canal (17) of water inlet (4), drainage valve lid (10) have make inhalant canal (17) and first cavity (12) be linked together interface channel (18).

6. A low resistance backflow preventer according to claim 5, wherein a sealing ring (19) is embedded between the drain valve cover (10) and the valve body (1) at the periphery of the connecting passage (18).

7. The low resistance backflow preventer according to claim 6, wherein the drain valve member (15) comprises a first valve member (20) disposed in the first chamber (12) and a second valve member (21) disposed in the second chamber (13), the diaphragm (11) is clamped between the first valve member (20) and the second valve member (21), the drain valve cover (10) has a guide hole, the first valve member (20) is inserted into the guide hole, the first valve member (20) is embedded with an O-ring (22) sealed on the inner wall of the guide hole, the drain passage is embedded with a cylindrical valve seat (23), the inner wall of the valve seat (23) has a convex ring (24), the valve seat (23) has a guide portion (25) for inserting the second valve member (21) and the outer wall of the guide portion (25) has a plurality of through holes (26) extending radially, a sealing gasket (27) is embedded in the end part of the second valve core (21), and the drainage spring (16) is sleeved outside the guide part (25) and provides elastic force to enable the second valve core (21) to have a tendency of being far away from the valve seat (23).

8. The low resistance backflow preventer according to claim 1 or 2 or 3 or 4, wherein the inlet check valve (2) and the outlet check valve (3) each comprise a check valve seat (28), a check housing (29), a check valve core (30) and a check spring (31), a sealing ring (32) is embedded in an outer wall of the check valve seat (28), the check housing (29) comprises a guide cylinder (291) and a connecting rib (292), the check valve core (30) passes through the guide cylinder (291), the connecting rib (292) is circumferentially and uniformly arranged on the guide cylinder (291) and fixedly connects the guide cylinder (291) and the housing (29), the check housing (29) has circumferentially and uniformly distributed check holes (293), the check spring (31) is sleeved outside the guide portion (25) and provides an elastic force so that the check valve core (30) always has a tendency to be sealed on the check valve seat (28), the end part of the check valve core (30) facing the check valve seat (28) is embedded with a rubber pad (33) and connected with a screw (34), and a pressing gasket (35) is arranged between the screw (34) and the rubber pad (33).

9. A low resistance backflow preventer according to claim 8, characterized in that the valve body (1) is connected with a water inlet ball valve (36) which is communicated with the water inlet (4), the valve cover (7) is connected with a valve cover ball valve (37) which is communicated with the middle chamber (5), and the valve body (1) is further connected with a water outlet ball valve (38) which is communicated with the water outlet (6).

10. A low resistance backflow preventer according to claim 9, wherein the water inlet (4) and the water outlet (6) are both connected with on-off valves (39) for controlling the on-off.

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