Medium-pressure energy-saving centrifugal fan capable of being accurately adjusted

Abstract

The invention discloses a medium-pressure energy-saving centrifugal fan capable of being accurately adjusted, and relates to the technical field of air circulation, the medium-pressure energy-saving centrifugal fan comprises a medium-pressure fan and a base, and the medium-pressure fan is fixedly arranged at the top of the base. The two air inlet pipes are arranged at the air inlet end of the centrifugal fan, the two air inlet pipes fixedly communicate with the air inlet end of the centrifugal fan through the vertical cylinder and the transition pipe, the two air inlet pipes are each provided with a filter screen, and the air inlet switching assembly is arranged in an inner cavity of the vertical cylinder; the air inlet switching assembly is used for controlling external air to enter the fan through any one of the two air inlet pipes, the air inlet pipes are provided with the timing blowback assemblies on the two sides of the filter screens, when one filter screen needs to be cleaned, the switching assembly controls the external air to enter the fan through the other air inlet pipe, the centrifugal fan cannot be crashed, and the service life of the centrifugal fan is prolonged. Meanwhile, the switching assembly can control the timing blowback assembly to wrap the two side faces of the filter screen through the follow-up assembly, a closed filter screen cleaning place is formed, and dust leakage cannot be caused.

Description

Technical Field

[0001] This invention relates to the field of air circulation technology, and in particular to a precisely adjustable medium-pressure energy-saving centrifugal fan. Background Technology

[0002] Medium-pressure energy-saving centrifugal fans are a type of fan equipment that combines moderate pressure output with high energy efficiency, and are widely used in industrial scenarios such as ventilation, dust removal, and cooling. This fan generates centrifugal force through impeller rotation, causing gas to enter axially and exit radially. It features moderate air pressure, stable air volume, and high operating efficiency. Compared to traditional fans, medium-pressure energy-saving centrifugal fans optimize aerodynamic structure and motor matching, effectively reducing energy consumption and noise, and extending service life. It is one of the important pieces of equipment for energy conservation and emission reduction in modern industry.

[0003] To prevent dust from entering the centrifugal fan, a screen is often installed at the axial air inlet. To prevent the screen from becoming clogged over time and affecting the airflow, it needs to be cleaned. In current technology, cleaning the screen usually requires workers to remove it from the centrifugal fan casing. This lack of a dedicated cleaning area can lead to dust leakage, and cleaning the screen can also cause the centrifugal fan to shut down, disrupting its continuous operation. Summary of the Invention

[0004] The purpose of this invention is to solve the problems in the prior art where cleaning the interception net usually requires workers to remove the interception net from the centrifugal fan casing. On the one hand, there is a lack of a dedicated place for cleaning the interception net, which leads to dust leakage during cleaning. On the other hand, cleaning the interception net can cause the centrifugal fan to shut down, delaying the continuous operation of the centrifugal fan. Therefore, this invention proposes a medium-pressure energy-saving centrifugal fan that can be precisely adjusted.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A precisely adjustable medium-pressure energy-saving centrifugal fan includes a medium-pressure fan and a base. The medium-pressure fan is fixedly installed on the top of the base. A vertical cylinder is fixedly installed at the air inlet end of the medium-pressure fan through a connecting pipe. Air inlet pipes are fixedly connected to both sides of the vertical cylinder. A filter screen is installed in the middle of the inner cavity of the air inlet pipe. The filter screen is used to pre-filter the air entering the fan. The top of the vertical cylinder is equipped with an air intake switching component, which is used to control the entry of external air into the fan through either of the two air intake pipes, so as to realize the switching control of the air intake path. The air intake pipe is equipped with timed backflushing components on both sides of the filter screen. The timed backflushing components are used to spray reverse airflow onto the filter screen at a set period to prevent airflow blockage caused by dust accumulation on the filter screen. The base has a storage box at the bottom of the vertical cylinder. The storage box stores intercepted water and performs liquid separation of dust in the backflushing gas.

[0006] Optionally, the intake switching assembly includes a timer motor, a switching cylinder, and a vertical shaft. The timer motor is fixedly mounted on the top of the vertical cylinder, the output end of the timer motor is fixedly mounted on the vertical shaft, and the switching cylinder is fixedly mounted on the vertical shaft.

[0007] Optionally, the timed backflush assembly includes a capture plate, a backflush plate, a waste pipe, a synchronous flipping assembly, a follow-up assembly, and an air supply assembly. The synchronous flipping assembly drives the capture plate and backflush plate inside the same air inlet pipe to open or close simultaneously. The follow-up assembly controls the timed backflush assembly to follow the air inlet switching assembly when it is activated. The air supply assembly provides an air source for the timed backflush assembly.

[0008] Optionally, the synchronous flipping assembly includes a bottom pulley, an end belt, and an end pulley. The air intake pipe is rotatably connected to a capture disc on one side of the filter screen, and the air intake pipe is rotatably connected to a common shaft on the other side of the filter screen. An end pulley is fixedly installed on the top of the capture disc's rotating shaft.

[0009] Optionally, a conical cavity is provided on the side of the capture plate, and a sludge outlet pipe is fixedly connected to the bottom of the capture plate. The bottom of the sludge outlet pipe is inserted into the inner cavity of the storage box. A replenishment pipe and a sludge outlet pipe are arranged sequentially along the vertical direction on the side of the storage box. A backflush plate is fixedly provided at the bottom of the common shaft, and a bottom pulley is fixedly provided at the bottom of the outer wall of the common shaft. An end belt is sleeved on the outer wall of the bottom pulley and the end pulley.

[0010] Optionally, the gas supply assembly includes a vertical pipe, a branch pipe, and a common pipe. A fixing plate is fixedly installed in the middle of the common pipe. The fixing plate is fixedly installed at the top of the vertical cylinder. Branch pipes are symmetrically fixedly installed on the side of the common pipe. The other end of the branch pipe is fixedly connected to the vertical pipe.

[0011] Optionally, the vertical tube is sleeved on the outer wall of the common shaft, and both the common shaft and the backflush disc are hollow. The common shaft has an air inlet hole on the side of the inner cavity of the vertical tube, and the backflush disc has a backflush hole on its side wall. The position of the backflush hole corresponds one-to-one with the position of the filter screen hole.

[0012] Optionally, the top of the switching cylinder is lower than the bottom of the intake pipe, the top of the switching cylinder has a circular array of AC slots, the side of the switching cylinder has an AC hole with the same diameter as the inner diameter of the intake pipe, and the bottom of the switching cylinder is closed.

[0013] Optionally, the diameters of the capture disc and the backflush disc are the same as the diameter of the inner cavity of the intake pipe, and the distance between the center of the capture disc and the center of the backflush disc is greater than the diameter of the filter screen.

[0014] Optionally, the follower assembly includes a double-groove pulley, a starting belt, and a top pulley, and the vertical shaft is fixedly provided with two grooves on the outer wall of the double-groove pulley at the top of the switching cylinder.

[0015] Optionally, the double-groove pulley has a starting belt fitted inside each of the two grooves, and a top pulley fitted at the other end of the starting belt. The top pulley is fixedly mounted on the top outer wall of the common shaft.

[0016] Compared with the prior art, the present invention has the following advantages: This invention features two intake pipes at the air inlet end of a centrifugal fan. These two intake pipes are fixedly connected to the air inlet end of the centrifugal fan via a vertical cylinder and a transition pipe. Both intake pipes are equipped with filters. An intake switching component is installed inside the vertical cylinder. This component controls the entry of external air into the fan through either of the two intake pipes. Timed backflushing components are installed on both sides of the filters on the intake pipes. When one filter needs cleaning, the switching component controls the external air to enter the fan through the other intake pipe, preventing the centrifugal fan from shutting down. Simultaneously, the switching component controls the timed backflushing component via a follow-up component to wrap around both sides of the filter, forming a sealed filter cleaning area and preventing dust leakage.

[0017] The core components of the timed backflushing assembly of this invention are a backflushing disc and a capture disc. An air supply component is provided on the common axis of the backflushing disc. When the synchronous flipping component drives the backflushing disc and the capture disc to rotate and wrap around the filter screen, the purely mechanical air supply component will automatically blow high-pressure gas onto the filter screen. The high-pressure gas carries the waste dust and is discharged into a storage tank containing intercepting water through the sewage outlet pipe at the bottom of the capture disc. The water curtain can effectively capture and settle dust particles, preventing them from being dispersed back into the air, thus achieving environmentally friendly and efficient wet dust removal.

[0018] The timed backflush assembly of the present invention also has the function of protecting the filter screen in standby mode. When the filter screen of an air intake pipe is in standby mode, the backflush disc and the capture disc in the timed backflush assembly can wrap around the filter screen to form a closed structure, effectively shielding and protecting the filter screen. This can prevent dust, moisture and other impurities in the air from adhering to the filter screen during standby, prevent it from getting damp, clogged or aging, and ensure that the filter screen is still in a clean and good working condition when it is restarted. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the overall structure of the present invention.

[0020] Figure 2 for Figure 1 A schematic diagram of the structure after removing the protective box.

[0021] Figure 3 for Figure 2 Another perspective structural diagram.

[0022] Figure 4 for Figure 3 A partial cross-sectional view of the vertical cylinder structure.

[0023] Figure 5 for Figure 4 A partial cross-sectional view of the intake pipe.

[0024] Figure 6 This is a structural schematic diagram of the switching cylinder and its connecting parts.

[0025] Figure 7 This is a schematic diagram of the timed backflush assembly.

[0026] Figure 8 for Figure 7 Another perspective structural diagram.

[0027] Figure 9 This is a structural diagram of the timed backflushing component and its connecting parts.

[0028] Figure 10 for Figure 9 Another perspective structural diagram.

[0029] In the diagram: 1. Protective box; 2. Medium-pressure fan; 3. Base; 4. Storage box; 41. Liquid replenishment pipe; 42. Liquid outlet pipe; 5. Connecting pipe; 6. Vertical cylinder; 61. Air inlet pipe; 7. Timer motor; 71. Vertical shaft; 8. Filter screen; 9. Double groove pulley; 10. Starting belt; 11. Top pulley; 12. Switching cylinder; 121. AC slot; 122. AC port; 13. Fixing plate; 14. Common pipe; 15. Diverter pipe; 16. Vertical pipe; 17. Capture plate; 171. Sewage outlet pipe; 18. Backflush plate; 181. Backflush port; 182. Common shaft; 1820. Air inlet port; 19. Bottom pulley; 20. End belt; 21. End pulley. Detailed Implementation

[0030] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0031] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0032] Reference Figure 1-10 A precisely adjustable medium-pressure energy-saving centrifugal fan includes a medium-pressure fan 2 and a base 3. The medium-pressure fan 2 is fixedly mounted on the top of the base 3. A vertical cylinder 6 is fixedly mounted on the air inlet end of the medium-pressure fan 2 through a connecting pipe 5. Air inlet pipes 61 are fixedly connected to both sides of the vertical cylinder 6. A filter screen 8 is installed in the middle of the inner cavity of the air inlet pipe 61. The filter screen 8 is used to pre-filter the air entering the fan. In order to protect the structure of the entire air inlet system, a protective box 1 is installed on the top of the air inlet end of the medium-pressure fan 2 by bolts on the base 3. The two ends of the air inlet pipe 61 extend from the sides of the protective box 1. The protective box 1 covers the air inlet end of the medium-pressure fan 2 and the air inlet pipe 61 assembly extending from both sides, forming a full-coverage protection for the functional components such as filtration, backflushing, and switching set on one side of the air inlet end, which plays a role in dust prevention, rain prevention, and corrosion prevention.

[0033] An air intake switching assembly is provided at the top of the vertical cylinder 6. The air intake switching assembly is used to control the entry of external air into the fan through either of the two air intake pipes 61, so as to realize the switching control of the air intake path. The air intake switching assembly includes a timer motor 7, a switching cylinder 12, and a vertical shaft 71. The timer motor 7 is fixedly installed at the top of the vertical cylinder 6 and extends out from the top of the protective box 1. The protective box 1 is provided with a circular hole at the corresponding position. The vertical shaft 71 is fixedly installed at the output end of the timer motor 7, and the switching cylinder 12 is fixedly installed on the vertical shaft 71.

[0034] The top of the switching cylinder 12 is lower than the bottom of the air inlet pipe 61. The top of the switching cylinder 12 has a circular array of AC slots 121, and the side of the switching cylinder 12 has an AC hole 122. The diameter of the AC hole 122 is the same as the inner diameter of the air inlet pipe 61. The bottom of the switching cylinder 12 is closed. Therefore, no matter what position the timer motor 7 drives the switching cylinder 12 to rotate, the inner cavity of the switching cylinder 12 can always be connected to the connecting pipe 5 on the side of the vertical cylinder 6 through the AC slot 121. Finally, the inner cavity of the switching cylinder 12 is connected to the air inlet of the medium-pressure fan 2, ensuring that the air intake path is not interrupted.

[0035] The timer motor 7 is a servo motor with a built-in timer, and the model can be iSV57-30. When the timer reaches its set time, the timer motor 7 can drive the switching cylinder 12, which is directly fixed to the vertical shaft 71, to rotate 180 degrees, so that the AC port 122 on the side of the switching cylinder 12 can be connected to any air intake pipe 61. The start time of the timer motor 7 can be set according to actual needs, thereby completing the switching of the air intake source of the medium pressure fan 2 and backflushing the filter screen 8.

[0036] The air intake pipe 61 is provided with timed backflush components on both sides of the filter screen 8. The timed backflush components are used to spray reverse airflow onto the filter screen 8 at a set period to prevent airflow blockage caused by dust accumulation on the filter screen 8. The timed backflush components include a capture plate 17, a backflush plate 18, a waste outlet pipe 171, a synchronous flipping component, a follow-up component, and an air supply component. The synchronous flipping component drives the capture plate 17 and the backflush plate 18 inside the same air intake pipe 61 to open or close simultaneously. The follow-up component controls the timed backflush component to follow the action of the air intake switching component. The air supply component provides an air source for the timed backflush component.

[0037] The synchronous flipping assembly includes a bottom pulley 19, an end belt 20, and an end pulley 21. An air inlet pipe 61 is rotatably connected to a capture plate 17 on one side of the filter screen 8, and a common shaft 182 is rotatably connected to the other side of the filter screen 8. An end pulley 21 is fixedly installed on the top of the shaft of the capture plate 17. A conical cavity is opened on the side of the capture plate 17, and a waste discharge pipe 171 is fixedly connected to the bottom of the capture plate 17. The bottom of the waste discharge pipe 171 is inserted into the inner cavity of the storage box 4. The conical cavity on the side of the capture plate 17 is a bucket-shaped cavity that is wider on one side and narrower on the other. The wide end of the conical cavity faces the side of the filter screen 8, and the narrow section of the conical cavity is connected to one end of the waste discharge pipe 171. When the filter screen 8 on one side of the capture plate 17 is back-blown, the conical cavity guides the back-blown dust to accumulate inside the waste discharge pipe 171.

[0038] The storage tank 4 has a replenishment pipe 41 and an outlet pipe 42 arranged vertically on its side. The replenishment pipe 41 replenishes the storage water into the inner cavity of the storage tank 4, and the outlet pipe 42 is used to discharge the waste intercepted liquid from the inner cavity of the storage tank 4. Valves are required in the inner cavities of both the outlet pipe 42 and the replenishment pipe 41, which are not shown in the figure.

[0039] A backflush disc 18 is fixedly installed at the bottom of the common shaft 182, and a bottom pulley 19 is fixedly installed at the bottom of the outer wall of the common shaft 182. An end belt 20 is sleeved on the outer wall of the bottom pulley 19 and the end pulley 21. The bottom pulley 19 and the end pulley 21 have the same diameter. Therefore, the backflush disc 18 and the capture disc 17 can rotate synchronously at the same angle through the bottom pulley 19, the end pulley 21, and the end belt 20.

[0040] A storage box 4 is set at the bottom of the vertical cylinder 6 on the base 3. The storage box 4 stores intercepted water and performs liquid separation of dust in the backflushing gas. The air supply component includes a vertical pipe 16, a branch pipe 15, and a common pipe 14. A fixing plate 13 is fixedly installed in the middle of the common pipe 14. The fixing plate 13 is fixedly installed on the top of the vertical cylinder 6. The branch pipes 15 are symmetrically fixed on the side of the common pipe 14. The other end of the branch pipe 15 is fixedly connected to the vertical pipe 16. The vertical pipe 16 is sleeved on the outer wall of the common shaft 182. One end of the common pipe 14 is in a closed state and the other end is in an open state. When in use, the open end of the common pipe 14 is connected to the external compressed air pipeline as a high-pressure gas input port.

[0041] Both the common shaft 182 and the backflush disc 18 are hollow. The common shaft 182 has an air inlet 1820 on the side of the inner cavity of the vertical tube 16. The backflush disc 18 has a backflush hole 181 on its side wall. The position of the backflush hole 181 corresponds one-to-one with the position of the hole in the filter screen 8. The diameter of the capture disc 17 and the backflush disc 18 is the same as the inner diameter of the air inlet tube 61. The distance between the center of the capture disc 17 and the center of the backflush disc 18 is greater than the diameter of the filter screen 8. When the capture disc 17 and the backflush disc 18 rotate synchronously to wrap around or open the filter screen 8, the capture disc 17 and the backflush disc 18 will not collide with the filter screen 8.

[0042] To further achieve linkage between the intake switching component and the timed backflushing component, a follow-up component is also provided. The follow-up component includes a double-grooved pulley 9, a starting belt 10, and a top pulley 11. The vertical shaft 71 is fixedly mounted on the top of the switching cylinder 12, and the outer wall of the double-grooved pulley 9 has two grooves. The starting belt 10 is fitted inside each of the two grooves of the double-grooved pulley 9. The other end of the starting belt 10 is fitted with the top pulley 11, which is fixedly mounted on the top outer wall of the common shaft 182. Therefore, when the vertical shaft 71 rotates, it will drive the two starting belts 10 to rotate. (Refer to...) Figure 8 The two sets of capture discs 17 and backflush discs 18 are positioned inside the two air intake pipes 61 as shown in the figure. When the timer motor 7 drives the switching cylinder 12 to the initial state, the AC hole 122 on the side of the switching cylinder 12 is connected to the unwrapped filter screen 8. The double groove pulley 9 drives the starting belt 10 to link with the top pulley 11, thereby realizing the synchronous rotation of the common shaft 182, driving the backflush disc 18 and capture disc 17 to flip, completing the air intake switching, and realizing the sealing and backflush operation of the filter screen 8 in the other channel.

[0043] The specific implementation steps and principles of this invention are as follows: In the initial state, one end of the common pipe 14 is connected to an external gas supply system, as shown in the reference. Figure 8 The backflush disc 18 and capture disc 17 inside one intake pipe 61 are in the closed state, while the backflush disc 18 and capture disc 17 inside the other intake pipe 61 are in the open state. Dust is intercepted by the filter screen 8 inside the intake pipe 61. The air inlet 1820 inside the intake pipe 61 (described later) is intersected with the diverter pipe 15, so high-pressure gas cannot be obtained. At this time, the AC port 122 on the side of the switching cylinder 12 is connected to the intake pipe 61 (described later), and the centrifugal fan obtains clean air through the intake pipe 61 (described later).

[0044] When the timer motor 7 starts, it drives the vertical shaft 71 to rotate. The vertical shaft 71 drives the AC port 122 on the side of the switching cylinder 12 to rotate until it is aligned with another air inlet pipe 61. The vertical shaft 71 drives the back-blowing disc 18 at the bottom of the common shaft 182 to rotate until it is parallel to the filter screen 8 that needs to be back-blown cleaned, through the double groove pulley 9, the starting belt 10, and the top pulley 11. At the same time, the back-blowing disc 18 drives the capture disc 17 to rotate until it is parallel to the filter screen 8, through the bottom pulley 19, the end pulley 21, and the end belt 20. The air inlet 1820 inside the external air inlet pipe 61 of the filter screen 8 is aligned with the diverter pipe 15 to obtain high-pressure gas. The high-pressure gas discharges the dust intercepted by the filter screen 8 through the capture disc 17 and the sewage outlet pipe 171 into the storage box 4. The dust is intercepted by the stored water in the inner cavity of the storage box 4.

[0045] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A precisely adjustable medium-pressure energy-saving centrifugal fan, comprising a medium-pressure fan and a base, characterized in that, A medium-pressure fan is fixedly installed on the top of the base. A vertical cylinder is fixedly installed at the air inlet end of the medium-pressure fan through a connecting pipe. Air inlet pipes are fixedly connected to both sides of the vertical cylinder. A filter screen is installed in the middle of the inner cavity of the air inlet pipe. The filter screen is used to pre-filter the air entering the fan. The top of the vertical cylinder is equipped with an air intake switching component, which is used to control the entry of external air into the fan through either of the two air intake pipes, so as to realize the switching control of the air intake path. The air intake pipe is equipped with timed backflushing components on both sides of the filter screen. The timed backflushing components are used to spray reverse airflow onto the filter screen at a set period to prevent airflow blockage caused by dust accumulation on the filter screen. The base has a storage box at the bottom of the vertical cylinder. The storage box stores intercepted water and performs liquid separation of dust in the backflushing gas.

2. The precisely adjustable medium-pressure energy-saving centrifugal fan according to claim 1, characterized in that, The intake switching assembly includes a timer motor, a switching cylinder, and a vertical shaft. The timer motor is fixedly mounted on the top of the vertical cylinder, and the output end of the timer motor is fixedly mounted on the vertical shaft. The switching cylinder is fixedly mounted on the vertical shaft.

3. The precisely adjustable medium-pressure energy-saving centrifugal fan according to claim 2, characterized in that, The timed backflush assembly includes a capture plate, a backflush plate, a waste outlet pipe, a synchronous flipping assembly, a follow-up assembly, and an air supply assembly. The synchronous flipping assembly drives the capture plate and backflush plate inside the same air inlet pipe to open or close simultaneously. The follow-up component enables the timed backflush component to follow the intake switching component when it operates, and the air supply component provides an air source for the timed backflush component.

4. The precisely adjustable medium-pressure energy-saving centrifugal fan according to claim 3, characterized in that, The synchronous flipping assembly includes a bottom pulley, an end belt, and an end pulley. The air intake pipe is rotatably connected to a capture disc on one side of the filter screen, and the air intake pipe is rotatably connected to a common shaft on the other side of the filter screen. An end pulley is fixedly installed on the top of the capture disc's rotating shaft.

5. A precisely adjustable medium-pressure energy-saving centrifugal fan according to claim 4, characterized in that, The capture plate has a conical cavity on its side, and a sludge outlet pipe is fixedly connected to the bottom of the capture plate. The bottom of the sludge outlet pipe is inserted into the inner cavity of the storage box. A replenishment pipe and a sludge outlet pipe are arranged in sequence along the vertical direction on the side of the storage box. A backflush plate is fixedly installed at the bottom of the common shaft. A bottom pulley is fixedly installed at the bottom of the outer wall of the common shaft. An end belt is sleeved on the outer wall of the bottom pulley and the end pulley.

6. A precisely adjustable medium-pressure energy-saving centrifugal fan according to claim 3, characterized in that, The gas supply assembly includes a vertical pipe, a branch pipe, and a common pipe. A fixing plate is fixedly installed in the middle of the common pipe. The fixing plate is fixedly installed at the top of the vertical cylinder. Branch pipes are symmetrically fixedly installed on the side of the common pipe. The other end of the branch pipe is fixedly connected to the vertical pipe.

7. A precisely adjustable medium-pressure energy-saving centrifugal fan according to claim 6, characterized in that, The vertical tube is sleeved on the outer wall of the common shaft. Both the common shaft and the backflush disc are hollow. The common shaft has an air inlet hole on the side of the inner cavity of the vertical tube. The backflush disc has a backflush hole on its side wall. The position of the backflush hole corresponds one-to-one with the position of the filter screen hole.

8. A precisely adjustable medium-pressure energy-saving centrifugal fan according to claim 2, characterized in that, The top of the switching cylinder is lower than the bottom of the intake pipe. The top of the switching cylinder has a circular array of AC slots. An AC hole is opened on the side of the switching cylinder. The diameter of the AC hole is the same as the inner diameter of the intake pipe. The bottom of the switching cylinder is closed.

9. A precisely adjustable medium-pressure energy-saving centrifugal fan according to claim 7, characterized in that, The diameters of the capture plate and the backflush plate are the same as the diameter of the inner cavity of the intake pipe, and the distance between the center of the capture plate and the center of the backflush plate is greater than the diameter of the filter screen.

10. A precisely adjustable medium-pressure energy-saving centrifugal fan according to claim 3, characterized in that, The follower assembly includes a double-groove pulley, a starting belt, and a top pulley. The vertical shaft is fixedly provided at the top of the switching cylinder, and the outer wall of the double-groove pulley has two grooves.

11. A precisely adjustable medium-pressure energy-saving centrifugal fan according to claim 10, characterized in that, The double-groove pulley has a starting belt fitted inside each of the two grooves, and a top pulley fitted at the other end of the starting belt. The top pulley is fixedly mounted on the top outer wall of the common shaft.

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