A backflow preventer detectable in a pressure reducing zone

Abstract

The application discloses a backflow preventer with a detectable decompression area, and relates to the technical field of backflow preventers.The backflow preventer comprises a main valve body, an inlet end stop valve, an outlet end stop valve, a blowdown dredging device and a secondary valve body.The backflow preventer is driven to move downward by a positive pressure difference formed by the recovery of the mixed medium after being discharged, and the filter dredging ring and the connecting rod are reset.The connecting rod drives the compression ring-shaped compression cavity to move downward, so that residual air in the compression ring-shaped compression cavity and clean liquid medium flowing back in the injection channel are squeezed into the injection channel and sprayed out of the outlet facing the filter screen section, thereby performing reverse gas-liquid blowing on the falling filter screen section layer by layer to spray impurities into the filter residue cavity.Meanwhile, the filter screen section is scraped with the arc corner scraping ring when the filter screen section descends, so that residual impurities are scraped off and introduced into the filter residue cavity along the arc-shaped slope, thereby realizing double self-cleaning of spraying and scraping, keeping the filter screen section transparent to reduce blockage and maintenance frequency, and unifying the removal of impurities and the filtration of impurities to complete directional collection in the filter residue cavity.

Description

Technical Field

[0001] This invention relates to the field of backflow prevention technology, specifically a backflow prevention device with detectable pressure reduction zone. Background Technology

[0002] A backflow preventer is a device installed on water supply pipelines to prevent backflow pollution. It is used to prevent the medium from flowing back upstream when the pipeline pressure is abnormal. When the upstream pressure drops suddenly or even becomes negative due to pipe bursts, water outages for maintenance, or fire-fighting water intake, a siphon may be generated, drawing the medium from equipment, storage tanks, or process pipelines back to the main pipe. When the downstream pressure is higher than the supply pressure due to the thermal expansion of the user-side booster pump or heat exchange system, or process pressurization, back pressure may be formed, pushing the medium back upstream. Therefore, the backflow preventer cuts off the reverse channel or guides the risky medium to a safe path through backflow prevention, pressure reduction isolation, and necessary discharge, thus avoiding pollution of the water quality at the source.

[0003] In existing backflow preventers, under backflow conditions, the backflowing medium often carries impurities such as mud, sand, and rust into the pressure reduction zone and discharge path, causing impurities to randomly deposit and adhere inside. This leads to wear, jamming, and blockage at uncertain locations in the pressure reduction zone and discharge port, resulting in poor discharge, seal failure, or continuous leakage. The backflow prevention performance and operational reliability are difficult to guarantee stably, and maintenance costs increase. Summary of the Invention

[0004] The purpose of this invention is to provide a backflow preventer with detectable pressure reduction zone, so as to solve the problem that the pressure reduction zone and discharge port of the backflow preventer are easily contaminated in the prior art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a backflow preventer with detectable pressure reduction zone, comprising a main valve body and a sewage drainage device, wherein an inlet shut-off valve is installed at the inlet of the main valve body, an outlet shut-off valve is installed at the outlet of the main valve body, and a secondary valve body is installed at the bottom of the main valve body. The sewage discharge and drainage device includes a drainage rod and a reset flushing assembly. The drainage rod is slidably installed in the main valve body. A baffle is installed at the bottom of the drainage rod, and a filter drainage ring is installed at the bottom of the baffle. The filter drainage ring is slidably connected to the secondary valve body. Several sewage discharge openers are installed at the bottom of the baffle, and the sewage discharge openers are slidably connected to the secondary valve body. The reset flushing assembly is installed in the secondary valve body and is connected to the bottom of the baffle. An elastic baffle is installed on the drainage rod and is connected to the top of the main valve body.

[0006] The backflow preventer is connected to an external control system, which is used to operate the entire backflow preventer.

[0007] A sensor is installed inside the main valve body, and the top of the guide rod passes through an elastic partition and connects to the sensor. The sensor is used to detect the displacement state of the guide rod and output a corresponding electrical signal to the control system. The sensor can be a displacement sensor, which converts the displacement of the guide rod into an electrical signal and transmits it to the control system. The control system analyzes the displacement of the guide rod to detect the pressure state in the pressure reduction zone of the main valve body.

[0008] The pressure-reducing zone of the main valve body is located between the inlet shut-off valve and the outlet shut-off valve.

[0009] The elastic partition has a plate in the middle, which is connected to the guide rod. An elastic membrane is provided around the plate, and the elastic membrane is connected to the top of the main valve body.

[0010] The secondary valve body is provided with a closed port, and the baffle can be fitted with the closed port. The secondary valve body is provided with a filter cake chamber, which is connected to the closed port. The bottom of the filter cake chamber is provided with several slag discharge ports, and several flexible membranes are installed on the top of the baffle. The sewage discharge switch includes a sleeve, which is installed at the bottom of the baffle and is movably connected to the slag discharge port. The bottom end of the sleeve passes through the slag discharge port and is equipped with a plug, which can be fitted into the bottom end of the slag discharge port. A slidable rod is installed inside the sleeve, and a return spring is installed between the slurry rod and the sleeve. The top end of the slurry rod passes through the baffle and abuts against the flexible membrane.

[0011] Furthermore, the unblocking rod includes a sliding rod, which is slidably installed inside the sleeve. Several levers are installed on the sliding rod, and the levers are movably connected to the sleeve. One end of the lever passes through the sleeve, and a contact is installed at the top of the sliding rod. The contact is slidably connected to the baffle, and the top of the contact abuts against the flexible membrane. A return spring is installed between the bottom of the contact and the sleeve.

[0012] When the backflow preventer is working normally and there is no backflow, the baffle and the closed port are engaged, which simultaneously drives the drain valve to descend. The sleeve drives the plug to disengage from the slag outlet, and the lever on the unblocking rod moves downward into the slag outlet. At this time, the slag outlet opens, and the impurities filtered out in the filter chamber fall and are discharged through the gap between the sleeve and the slag outlet. When the baffle and the closed port are engaged, the flexible membrane on it is located at the bottom of the pressure-reducing zone. When the medium continues to pass through the pressure-reducing zone, the water pressure generated will act on the flexible membrane. The flexible membrane transmits the pressure to the contact. After being pressed, the contact squeezes the return spring downward, and drives several levers to move downward through the slide rod. Because the water pressure of the flowing medium is fluctuating, when the water pressure is relatively weakened, the return spring rebounds and drives the levers to move upward through the contact. This achieves the purpose of using water pressure fluctuations to make the levers move up and down near the slag outlet. The levers move up and down and back and forth near the slag outlet to move the remaining impurities, so that the impurities are quickly discharged from the filter chamber through the slag outlet, achieving the effect of accelerating the discharge of impurities and preventing blockage.

[0013] Furthermore, the secondary valve body is provided with a retraction chamber, and an arc-shaped scraper ring is provided on the secondary valve body. The filter guide ring is slidably installed in the retraction chamber, and a drop port is opened on the axis of the secondary valve body.

[0014] Furthermore, the filter guide ring has a solid section, which is installed at the bottom of the baffle, and a filter screen section is located at the bottom of the solid section.

[0015] The filter screen has several filter holes, which are used to block impurities in the mixed medium while allowing the clean medium to pass through.

[0016] When the baffle moves upward due to the backflow pressure difference, it will simultaneously drive the filter guide ring and the drain valve to move upward. After moving upward a certain distance, the plug on the sleeve engages with the slag outlet, the slag outlet is blocked, and the baffle stops moving. At this time, the filter guide ring slides out of the retraction chamber, and the filter screen segment on the filter guide ring is located at the top of the filter slag chamber. When the mixed medium enters the filter slag chamber through the closed port, the clean medium passes through the filter screen segment and is discharged from the lower port, while the filtered impurities remain in the filter slag chamber. This achieves the effect of filtering the mixed medium before discharge, which is beneficial for the subsequent recycling of the discharged medium and also avoids the arbitrary adhesion of impurities, which can cause uncertain wear and blockage to the valve body.

[0017] Furthermore, the secondary valve body is provided with an annular compression chamber, and the secondary valve body is provided with several injection channels. The injection channels surround the outside of the annular compression chamber and are connected to the annular compression chamber. The reset flushing assembly is installed inside the annular compression chamber.

[0018] Furthermore, the filter guide ring includes a compression ring, which is slidably installed in the annular compression chamber. A compression spring is installed between the compression ring and the annular compression chamber. Several connecting rods are installed on the compression ring, and the connecting rods are slidably connected to the secondary valve body. The top of the connecting rods passes through the annular compression chamber and is connected to the baffle.

[0019] After the mixed medium is discharged, the control system resumes medium delivery. Under the action of positive pressure differential, the baffle descends again, driving the filter guide ring and connecting rod to descend as well. The connecting rod descends and compresses the compression spring through the compression ring. At the same time, the medium in the annular compression chamber is also squeezed into the injection channel as it is compressed. The injection medium includes the air originally remaining in the annular compression chamber, as well as some clean liquid medium that flows back into the injection channel during the discharge of the mixed medium. The outlet of the injection channel faces the filter screen section, and the compressed and ejected gas-liquid mixture reverses the flow layer by layer through the continuously falling filter screen section. During the purging process, the impurities blown out are sprayed into the filter cake chamber. At the same time, as the filter screen section descends, its filter surface scrapes against the arc-shaped corner at the top of the arc-shaped scraper ring, removing the remaining impurities. The scraped impurities are then guided into the filter cake chamber by the arc-shaped inclined surface on the arc-shaped corner. This achieves dual cleaning of the filter screen section through gas-liquid mixed spray washing and arc-shaped scraping, keeping the filter screen section highly clean, preventing impurities from clogging it, and reducing maintenance frequency. Furthermore, the removed impurities are uniformly sprayed into or guided into the filter cake chamber and collected together with the filtered impurities, completing the targeted collection of impurities from multiple sources.

[0020] Furthermore, the inlet shut-off valve includes a first valve ring, which is installed at the inlet of the main valve body. A first valve stem is slidably mounted on the first valve ring. One end of the first valve stem passes through the first valve ring and is fitted with a first valve plate. A first spring is installed between the first valve stem and the first valve ring.

[0021] During operation, the external pipeline delivers clean media to the main valve body. Part of the media enters the regulating chamber through the connecting channel. The other part of the media flows to the inlet shut-off valve. Under water pressure, the first valve plate drives the first valve stem to slide on the first valve ring, the first spring is compressed, the first valve plate separates from the first valve ring, the inlet is opened, and the media enters the pressure reducing zone after passing through the first valve ring.

[0022] When the medium enters the pressure reducing zone, the water pressure decreases due to the obstruction of the inlet shut-off valve. At this time, the water pressure in the pressure reducing zone is less than the water pressure at the inlet of the main valve body. Since the connecting channel is connected to the inlet, the water pressure of the medium entering the regulating chamber is the same as that at the inlet, both of which are greater than the water pressure in the pressure reducing zone. Under the action of the pressure difference, the elastic baffle is squeezed downward toward the pressure reducing zone. The elastic baffle drives the guide rod to move downward, and the guide rod drives the baffle to engage with the closing port, completing the sealing of the secondary valve body, so that the medium in the pressure reducing zone cannot enter the secondary valve body.

[0023] Furthermore, the outlet shut-off valve includes a second valve stem, a second valve ring, and a third valve ring. The second valve ring and the third valve ring are both installed at the water outlet end of the main valve body. The second valve stem is slidably installed between the second valve ring and the third valve ring. A second valve plate is installed on the second valve stem, and a second spring is installed between the second valve plate and the third valve ring.

[0024] The medium entering the pressure-reducing zone flows to the outlet shut-off valve. Under the further action of water pressure, the pressurized second valve plate drives the second valve stem to slide on the second and third valve rings. The second spring is compressed, and the second valve plate separates from the second valve ring. The medium flows through the second and third valve rings in sequence into the next section of the pipeline.

[0025] When backflow occurs, the water pressure at the outlet is greater than that at the inlet. The medium flows backward from the outlet into the pressure-reducing zone. Due to the reverse water pressure, the valve body slides back to reset and seals the second valve ring again, thus blocking the backflow. During this period, some of the backflow medium will enter the pressure-reducing zone before the second valve ring is sealed, causing the water pressure in the pressure-reducing zone to rise and exceed the water pressure at the inlet and regulating chamber, generating a reverse pressure difference. Under the action of the reverse pressure difference, the first valve plate slides backward to seal the first valve ring, preventing the mixed medium containing the backflow medium from entering the inlet and thus contaminating the source medium.

[0026] Simultaneously, under the influence of reverse pressure differential and the rebound force exerted by the compression spring through the compression ring and connecting rod, the elastic baffle lifts the guide rod upwards. The guide rod then causes the baffle to disengage from the closed port, opening the port and allowing the mixed medium in the pressure-reducing zone to enter the secondary valve body. When the guide rod lifts upwards and generates displacement, the sensor converts the displacement into an electrical signal and outputs it to the control system. After the control system analyzes the upward displacement of the guide rod, it temporarily cuts off the medium delivery. Once the mixed medium in the pressure-reducing zone is discharged, the medium delivery is resumed.

[0027] Furthermore, the main valve body is provided with a connecting channel, and the elastic baffle and the top of the main valve body form an adjustment chamber, which is connected to the connecting channel.

[0028] Compared with the prior art, the beneficial effects of the present invention are: 1. The backflow pressure difference drives the baffle to move upward and simultaneously drives the filter guide ring and the drain valve to move upward, so that the sleeve plug engages with the slag outlet to first block the slag outlet and limit the stroke of the baffle. Then the filter guide ring slides out of the retraction chamber and positions its filter screen section at the top of the filter cake chamber. The mixed medium entering the filter cake chamber through the closed port first passes through the filter screen section to achieve solid-liquid separation: the clean medium passes through the filter screen section and is discharged from the lower outlet, while impurities are retained in the filter cake chamber. This achieves the purpose of filtering before discharge, which facilitates the recycling of the discharged medium and reduces the risk of wear and blockage caused by impurities randomly adhering in the valve body.

[0029] 2. The positive pressure difference generated by the restoration of forward conveying after the mixed medium is drained drives the baffle to descend and resets the filter guide ring and connecting rod. The descending connecting rod compresses the annular compression chamber, forcing the residual air and the clean liquid medium returning from the spray channel into the spray channel and spraying it out from the outlet towards the filter screen section. This performs layer-by-layer reverse gas-liquid purging on the falling filter screen section, spraying impurities into the filter cake chamber. At the same time, the scraping action of the arc-angle scraper ring during the descent of the filter screen section removes residual impurities and guides them into the filter cake chamber along the arc-shaped slope. This achieves dual self-cleaning through spraying and scraping, keeping the filter screen section clear to reduce clogging and maintenance frequency. The removed and filtered impurities are then uniformly guided into the filter cake chamber for directional collection.

[0030] 3. When there is no backflow, the baffle and the closed port are engaged, which causes the drain opening and closing device to move downward. This causes the sleeve plug to disengage from the slag outlet and drives the unblocking rod to enter the slag outlet to open the slag discharge channel. This allows impurities in the filter slag chamber to fall and be discharged along the gap between the sleeve and the slag outlet. At the same time, the flexible membrane on the baffle is located at the bottom of the pressure reduction zone and is affected by the water pressure fluctuation of the flowing medium. The pressure change is transmitted through the contact and slide bar, and the rod moves up and down near the slag outlet under the action of the return spring. This continuously disturbs the residual impurities and promotes their rapid passage through the slag outlet for discharge, thereby accelerating slag discharge and reducing the risk of slag outlet blockage.

[0031] 4. The inlet shut-off valve is used to throttle and reduce the pressure of the medium entering the pressure-reducing zone, so that the water pressure in the pressure-reducing zone is less than the water pressure at the inlet and the regulating chamber connected to it. Then, the pressure difference between the regulating chamber and the pressure-reducing zone is used to push the elastic baffle to squeeze and displace towards the pressure-reducing zone, and drive the guide rod to drive the baffle to fit and seal the secondary valve body channel with the closing port, so as to automatically block the medium in the pressure-reducing zone from entering the secondary valve body without the need for external power.

[0032] 5. When backflow occurs, the reverse water pressure pushes the valve body to reset and seal the second valve ring to cut off the backflow. The reverse pressure difference formed by the short-term backflow pressure increase in the pressure-reducing zone drives the first valve plate to seal the first valve ring to isolate the contaminant. At the same time, under the action of the reverse pressure difference and the spring rebound force, the guide rod is lifted to open the closing port, and the mixed medium in the pressure-reducing zone is introduced into the auxiliary valve body for discharge. The control system is triggered by the sensor to briefly stop the supply, and after the discharge is completed, the liquid supply is resumed, realizing the interlocking control of blocking, isolation and discharge. Attached Figure Description

[0033] Figure 1 This is a perspective view of the backflow preventer of the present invention; Figure 2 This is a cross-sectional view of the backflow preventer of the present invention; Figure 3 This is an elevation view of the sewage drainage device and the auxiliary valve body of the present invention; Figure 4 This is a cross-sectional view of the sewage drainage device and the auxiliary valve body of the present invention; Figure 5 This is a cross-sectional view of the secondary valve body of the present invention; Figure 6 For the present invention Figure 4 A magnified view of a portion of region A in the middle; Figure 7 This is a cross-sectional view of the sewage discharge switch of the present invention; Figure 8 This is a perspective view of the filter guide ring and reset flushing assembly of the present invention; Figure 9 For the present invention Figure 4 A magnified view of a portion of region B in the middle.

[0034] In the diagram: 1. Main valve body; 2. Inlet shut-off valve; 3. Outlet shut-off valve; 4. Sewage drainage device; 5. Secondary valve body; 21. First valve ring; 22. First valve stem; 23. First valve plate; 24. First spring; 31. Second valve ring; 32. Third valve ring; 33. Second valve stem; 34. Second valve plate; 35. Second spring; 41. Elastic partition; 42. Drainage rod; 43. Baffle; 44. Sewage discharge switch; 45. Reset flushing assembly; 46. Adjustment chamber; 47. Sensor; 48. Connection channel ; 49. Filter guide ring; 51. Closure port; 52. Filter cake chamber; 53. Slag discharge port; 54. Annular compression chamber; 55. Retraction chamber; 56. Spray channel; 57. Arc-angle scraper ring; 58. Drop port; 431. Flexible membrane; 441. Sleeve; 442. Plug; 443. Unclogging rod; 444. Return spring; 4431. Toggle rod; 4432. Contact; 4433. Slide rod; 451. Connecting rod; 452. Compression ring; 453. Compression spring; 491. Solid section; 492. Filter screen section. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] Example: Figures 1-9 As shown, the present invention provides a technical solution: a backflow preventer with detectable pressure reduction zone, comprising a main valve body 1 and a sewage drainage device 4. An inlet shut-off valve 2 is installed at the inlet of the main valve body 1, an outlet shut-off valve 3 is installed at the outlet of the main valve body 1, and a secondary valve body 5 is installed at the bottom of the main valve body 1. The sewage discharge device 4 includes a discharge rod 42 and a reset flushing assembly 45. The discharge rod 42 is slidably installed inside the main valve body 1. A baffle 43 is installed at the bottom of the discharge rod 42. A filter discharge ring 49 is installed at the bottom of the baffle 43. The filter discharge ring 49 is slidably connected to the secondary valve body 5. Several sewage discharge openers 44 are installed at the bottom of the baffle 43. The sewage discharge openers 44 are slidably connected to the secondary valve body 5. The reset flushing assembly 45 is installed inside the secondary valve body 5. The reset flushing assembly 45 is connected to the bottom of the baffle 43. An elastic baffle 41 is installed on the discharge rod 42. The elastic baffle 41 is connected to the top of the main valve body 1.

[0037] The backflow preventer is connected to an external control system, which is used to operate the entire backflow preventer.

[0038] A sensor 47 is installed inside the main valve body 1. The top end of the guide rod 42 passes through the elastic partition 41 and is connected to the sensor 47. The sensor 47 is used to detect the displacement state of the guide rod 42 and output a corresponding electrical signal to the control system. The sensor 47 can be a displacement sensor 47. The displacement sensor 47 converts the displacement of the guide rod 42 into an electrical signal and transmits it to the control system. The control system analyzes the displacement of the guide rod 42 to detect the pressure state of the pressure reduction zone of the main valve body 1.

[0039] The pressure reducing zone of the main valve body 1 is located between the inlet shut-off valve 2 and the outlet shut-off valve 3.

[0040] The elastic partition 41 has a plate body in the middle, which is connected to the guide rod 42. An elastic membrane is provided around the plate body, and the elastic membrane is connected to the top of the main valve body 1.

[0041] The inlet shut-off valve 2 includes a first valve ring 21, which is installed at the inlet of the main valve body 1. A first valve stem 22 is slidably mounted on the first valve ring 21. One end of the first valve stem 22 passes through the first valve ring 21 and is mounted on a first valve plate 23. A first spring 24 is installed between the first valve stem 22 and the first valve ring 21.

[0042] The outlet shut-off valve 3 includes a second valve stem 33, a second valve ring 31, and a third valve ring 32. The second valve ring 31 and the third valve ring 32 are both installed at the outlet end of the main valve body 1. The second valve stem 33 is slidably installed between the second valve ring 31 and the third valve ring 32. A second valve plate 34 is installed on the second valve stem 33. A second spring 35 is installed between the second valve plate 34 and the third valve ring 32.

[0043] The main valve body 1 is provided with a connecting channel 48. The elastic partition 41 and the top of the main valve body 1 form an adjustment chamber 46, which is connected to the connecting channel 48.

[0044] The secondary valve body 5 has a retraction chamber 55 inside, an arc-shaped scraper ring 57 on the secondary valve body 5, a filter guide ring 49 is slidably installed in the retraction chamber 55, and a drop opening 58 is opened on the axis of the secondary valve body 5.

[0045] A solid section 491 is provided on the filter guide ring 49. The solid section 491 is installed at the bottom of the baffle 43. A filter screen section 492 is provided at the bottom of the solid section 491.

[0046] The filter segment 492 has several filter holes, which are used to block impurities in the mixed medium while allowing the clean medium to pass through.

[0047] The secondary valve body 5 is provided with an annular compression chamber 54 and a number of injection channels 56. The injection channels 56 surround the outer side of the annular compression chamber 54 and are connected to the annular compression chamber 54. The reset flushing assembly 45 is installed in the annular compression chamber 54.

[0048] The filter guide ring 49 includes a compression ring 452, which is slidably installed in the annular compression chamber 54. A compression spring 453 is installed between the compression ring 452 and the annular compression chamber 54. Several connecting rods 451 are installed on the compression ring 452. The connecting rods 451 are slidably connected to the secondary valve body 5. The top end of the connecting rod 451 passes through the annular compression chamber 54 and is connected to the baffle 43.

[0049] The secondary valve body 5 is provided with a closed port 51, and the baffle 43 can be fitted with the closed port 51. The secondary valve body 5 is provided with a filter cake chamber 52, which is connected to the closed port 51. The bottom of the filter cake chamber 52 is provided with several slag discharge ports 53, and the top of the baffle 43 is equipped with several flexible membranes 431. The sewage discharge switch 44 includes a sleeve 441, which is installed at the bottom of the baffle 43. The sleeve 441 is movably connected to the slag discharge port 53. The bottom end of the sleeve 441 passes through the slag discharge port 53 and is fitted with a plug 442. The plug 442 can be fitted into the bottom end of the slag discharge port 53. A slidable rod 443 is installed inside the sleeve 441. A return spring 444 is installed between the slidable rod 443 and the sleeve 441. The top end of the slidable rod 443 passes through the baffle 43 and abuts against the flexible membrane 431.

[0050] The unblocking rod 443 includes a sliding rod 4433, which is slidably installed inside the sleeve 441. Several levers 4431 are installed on the sliding rod 4433, and the levers 4431 are movably connected to the sleeve 441. One end of the lever 4431 passes through the sleeve 441. A contact 4432 is installed at the top of the sliding rod 4433, and the contact 4432 is slidably connected to the baffle 43. The top of the contact 4432 abuts against the flexible membrane 431, and a return spring 444 is installed between the bottom of the contact 4432 and the sleeve 441.

[0051] The working principle of this invention is as follows: During operation, an external pipeline delivers clean media to the main valve body 1. Part of the media enters the regulating chamber 46 through the connecting channel 48. The other part of the media flows to the inlet shut-off valve 2. Under water pressure, the first valve plate 23 drives the first valve stem 22 to slide on the first valve ring 21, compressing the first spring 24. The first valve plate 23 separates from the first valve ring 21, opening the inlet. The media then passes through the first valve ring 21 and enters the pressure reducing zone.

[0052] When the medium enters the pressure reducing zone, the water pressure decreases due to the obstruction of the inlet shut-off valve 2. At this time, the water pressure in the pressure reducing zone is less than the water pressure at the inlet of the main valve body 1. Since the connecting channel 48 is connected to the inlet, the water pressure of the medium entering the regulating chamber 46 is the same as the water pressure at the inlet, both of which are greater than the water pressure in the pressure reducing zone. Under the action of the pressure difference between the two, the elastic baffle 41 is squeezed downward toward the pressure reducing zone. The elastic baffle 41 drives the guide rod 42 to move downward. The guide rod 42 drives the baffle 43 to engage with the closing port 51, completing the sealing of the secondary valve body 5, so that the medium in the pressure reducing zone cannot enter the secondary valve body 5.

[0053] The medium entering the pressure reduction zone flows to the outlet shut-off valve 3. Under the further action of water pressure, the pressurized second valve plate 34 drives the second valve stem 33 to slide on the second valve ring 31 and the third valve ring 32. The second spring 35 is compressed, the second valve plate 34 separates from the second valve ring 31, and the medium flows into the next section of the pipeline through the second valve ring 31 and the third valve ring 32 in sequence.

[0054] When backflow occurs, the water pressure at the outlet is greater than that at the inlet, and the medium flows back into the pressure-reducing zone from the outlet. Due to the reverse water pressure, the valve body slides back to reset and seals the second valve ring 31 again, thus blocking the backflow. During this period, some backflow medium will enter the pressure-reducing zone before the second valve ring 31 is sealed, causing the water pressure in the pressure-reducing zone to rise and exceed the water pressure at the inlet and regulating chamber 46, generating a reverse pressure difference. Under the action of the reverse pressure difference, the first valve plate 23 slides back to seal the first valve ring 21, preventing the mixed medium containing the backflow medium from entering the inlet and thus contaminating the source medium.

[0055] Simultaneously, under the reverse pressure difference and the rebound force applied by the compression spring 453 through the compression ring 452 and connecting rod 451, the elastic baffle 41 is driven to lift the guide rod 42 upward. The guide rod 42 drives the baffle 43 to disengage from the closed port 51, opening the closed port 51, and the mixed medium in the pressure-reducing zone enters the secondary valve body 5 from the closed port 51. When the guide rod 42 lifts upward and generates displacement, the sensor 47 converts the displacement into an electrical signal and outputs it to the control system. After the control system analyzes that the guide rod 42 has moved upward, it temporarily cuts off the medium delivery. After the mixed medium in the pressure-reducing zone is discharged, the medium delivery is resumed.

[0056] When the baffle 43 moves upward due to the backflow pressure difference, it will simultaneously drive the filter guide ring 49 and the drain switch 44 to move upward. After moving upward a certain distance, the plug 442 on the sleeve 441 engages with the slag outlet 53, the slag outlet 53 is blocked, and the baffle 43 stops moving. At this time, the filter guide ring 49 slides out of the retraction chamber 55, and the filter screen segment 492 on the filter guide ring 49 is located at the top of the filter cake chamber 52. When the mixed medium enters the filter cake chamber 52 through the closed port 51, the clean medium passes through the filter screen segment 492 and is discharged from the lower outlet 58. The filtered impurities are retained in the filter cake chamber 52, thereby achieving the effect of filtering the mixed medium first and then discharging it, which is conducive to the subsequent recycling of the discharged medium, and also avoids the arbitrary adhesion of impurities causing uncertain wear and blockage to the valve body.

[0057] After the mixed medium is discharged, the control system resumes medium delivery. Under the action of positive pressure differential, the baffle 43 descends again, driving the filter guide ring 49 and connecting rod 451 to descend. The connecting rod 451 descends and compresses the compression spring 453 through the compression ring 452. At the same time, the medium in the annular compression chamber 54 is also squeezed into the injection channel 56 as it is compressed. The injection medium includes the air that was originally left in the annular compression chamber 54, as well as some of the clean liquid medium that flows back into the injection channel 56 when the mixed medium is discharged. The outlet of the injection channel 56 faces the filter section 492, and the compressed gas-liquid mixture compresses the continuously falling filter section 492. 2. Layer-by-layer reverse purging is performed, and the impurities blown out are sprayed into the filter cake chamber 52. At the same time, when the filter screen section 492 descends, its filter surface will scrape against the arc-shaped corner at the top of the arc-shaped scraper ring 57, so that the residual impurities are scraped off. The scraped impurities are guided into the filter cake chamber 52 by the arc-shaped inclined surface on the arc-shaped corner, thereby achieving dual cleaning of the filter screen section 492 by gas-liquid mixed spray washing and arc-shaped scraping, so that the filter screen section 492 can be kept highly clean, avoiding impurity blockage and reducing maintenance frequency. In addition, the removed impurities are uniformly sprayed into or guided into the filter cake chamber 52 and collected together with the filtered impurities, completing the directional collection of impurities from multiple aspects.

[0058] When the backflow preventer is working normally and there is no backflow, the baffle 43 and the closing port 51 are engaged, which simultaneously drives the sewage discharge opening and closing device 44 to descend. The sleeve 441 drives the plug 442 to disengage from the slag discharge port 53. The lever 4431 on the unblocking rod 443 moves downward to the slag discharge port 53. At this time, the slag discharge port 53 opens, and the impurities filtered down in the filter slag chamber 52 fall and are discharged along the gap between the sleeve 441 and the slag discharge port 53. When the baffle 43 is engaged with the closed opening 51, the flexible membrane 431 on it is located at the bottom of the pressure-reducing zone. When the medium continues to pass through the pressure-reducing zone, the water pressure generated will act on the flexible membrane 431. The flexible membrane 431 transmits the pressure to the contact 4432. After being pressed, the contact 4432 squeezes the return spring 444 downward and drives several levers 4431 to move downward through the slide rod 4433. Since the water pressure of the flowing medium is fluctuating, when the water pressure is relatively weakened, the return spring 444 rebounds and drives the levers 4431 to move upward through the contact 4432. This achieves the purpose of using the water pressure fluctuation to make the levers 4431 move up and down near the slag outlet 53. The levers 4431 move the remaining impurities up and down near the slag outlet 53, so that the impurities are quickly discharged from the filter cake chamber 52 through the slag outlet 53, thereby accelerating the discharge of impurities and preventing blockage.

[0059] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A backflow preventer with detectable pressure reduction zone, characterized in that: The backflow preventer includes a main valve body (1) and a sewage drainage device (4). The main valve body (1) is equipped with an inlet shut-off valve (2) at the inlet and an outlet shut-off valve (3) at the outlet. The main valve body (1) is equipped with a secondary valve body (5) at the bottom. The sewage drainage device (4) includes a drainage rod (42) and a reset flushing assembly (45). The drainage rod (42) is slidably installed in the main valve body (1). A baffle (43) is installed at the bottom end of the drainage rod (42). A filter drainage ring (49) is installed at the bottom end of the baffle (43). The filter drainage ring (49) is slidably connected to the secondary valve body (5). Several sewage opening and closing devices (44) are installed at the bottom end of the baffle (43). The sewage opening and closing devices (44) are slidably connected to the secondary valve body (5). The reset flushing assembly (45) is installed in the secondary valve body (5). The reset flushing assembly (45) is connected to the bottom end of the baffle (43). An elastic partition (41) is installed on the drainage rod (42). The elastic partition (41) is connected to the top end of the main valve body (1).

2. The backflow preventer with detectable pressure reduction zone according to claim 1, characterized in that: The sub-valve body (5) is provided with a closed opening (51), and the baffle (43) can be fitted with the closed opening (51). The sub-valve body (5) is provided with a filter cake chamber (52), which is connected to the closed opening (51). The bottom of the filter cake chamber (52) is provided with several slag discharge ports (53), and the top of the baffle (43) is equipped with several flexible membranes (431). The drain opening / closing device (44) includes a sleeve (441), which is installed at the bottom of the baffle (43). The sleeve (441) is movably connected to the slag outlet (53). The bottom end of the sleeve (441) passes through the slag outlet (53) and is fitted with a plug (442). The plug (442) can be fitted into the bottom end of the slag outlet (53). A drain rod (443) is slidably installed inside the sleeve (441). A return spring (444) is installed between the drain rod (443) and the sleeve (441). The top end of the drain rod (443) passes through the baffle (43) and abuts against the flexible membrane (431).

3. A backflow preventer with detectable pressure reduction zone according to claim 2, characterized in that: The unblocking rod (443) includes a sliding rod (4433), which is slidably installed inside a sleeve (441). Several levers (4431) are installed on the sliding rod (4433), and the levers (4431) are movably connected to the sleeve (441). One end of the lever (4431) passes through the sleeve (441). A contact (4432) is installed at the top of the sliding rod (4433), and the contact (4432) is slidably connected to a baffle (43). The top of the contact (4432) abuts against a flexible membrane (431), and a return spring (444) is installed between the bottom of the contact (4432) and the sleeve (441).

4. A backflow preventer with detectable pressure reduction zone according to claim 2, characterized in that: The secondary valve body (5) is provided with a retraction cavity (55), and the secondary valve body (5) is provided with an arc-shaped scraper ring (57). The filter guide ring (49) is slidably installed in the retraction cavity (55), and the secondary valve body (5) has a drop opening (58) on its axis.

5. A backflow preventer with detectable pressure reduction zone according to claim 4, characterized in that: The filter guide ring (49) is provided with a solid section (491), the solid section (491) is installed at the bottom of the baffle (43), and the bottom of the solid section (491) is provided with a filter screen section (492).

6. A backflow preventer with detectable pressure reduction zone according to claim 2, characterized in that: The sub-valve body (5) is provided with an annular compression chamber (54), and the sub-valve body (5) is provided with a plurality of injection channels (56). The plurality of injection channels (56) surround the outside of the annular compression chamber (54), and the injection channels (56) are connected to the annular compression chamber (54). The reset flushing assembly (45) is installed in the annular compression chamber (54).

7. A backflow preventer with detectable pressure reduction zone according to claim 6, characterized in that: The filter guide ring (49) includes a compression ring (452), which is slidably installed in the annular compression chamber (54). A compression spring (453) is installed between the compression ring (452) and the annular compression chamber (54). Several connecting rods (451) are installed on the compression ring (452). The connecting rods (451) are slidably connected to the secondary valve body (5). The top end of the connecting rod (451) passes through the annular compression chamber (54) and is connected to the baffle (43).

8. A backflow preventer with detectable pressure reduction zone according to claim 1, characterized in that: The inlet shut-off valve (2) includes a first valve ring (21), which is installed at the inlet of the main valve body (1). A first valve stem (22) is slidably installed on the first valve ring (21). One end of the first valve stem (22) passes through the first valve ring (21) and is fitted with a first valve plate (23). A first spring (24) is installed between the first valve stem (22) and the first valve ring (21).

9. A backflow preventer with detectable pressure reduction zone according to claim 1, characterized in that: The outlet shut-off valve (3) includes a second valve stem (33), a second valve ring (31) and a third valve ring (32). The second valve ring (31) and the third valve ring (32) are both installed at the outlet end of the main valve body (1). The second valve stem (33) is slidably installed between the second valve ring (31) and the third valve ring (32). A second valve plate (34) is installed on the second valve stem (33). A second spring (35) is installed between the second valve plate (34) and the third valve ring (32).

10. A backflow preventer with detectable pressure reduction zone according to claim 1, characterized in that: The main valve body (1) is provided with a connecting channel (48), and the elastic partition (41) and the top of the main valve body (1) form an adjustment cavity (46), which is connected to the connecting channel (48).

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