Aerodynamic transmission device for fan outlet check door

Abstract

This utility model relates to the technical field of flue gas system equipment in industries such as power plants, metallurgy, and cement, and discloses a pneumatic transmission device for a fan outlet check valve. The device includes a check valve body, a primary transmission mechanism, a secondary transmission mechanism, a pneumatic drive assembly, and a pneumatic control cabinet. The check valve body is adapted to the large-size flue gas duct at the outlet of a 600MW or larger unit fan. This two-stage transmission structure amplifies the driving torque by 3-4 times by extending the lever arm (the length of the driving arm is adapted to the width of the flue gas duct), allowing a Φ350mm cylinder to output a torque of 60-80KNm, easily meeting the opening requirements under a maximum back pressure of 4.5KPa. Simultaneously, the crank arm is forged from alloy steel and reinforced with ribs, the primary rotating shaft is heat-treated and chrome-plated, and the support bearing is a deep groove ball bearing, ensuring structural strength and wear resistance under high torque transmission. The device has a continuous operating life exceeding 100,000 opening and closing cycles, and its reliability is 60% higher than that of traditional direct drives.

Description

Technical Field

[0001] This utility model relates to the technical field of flue gas system equipment in industries such as power plants, metallurgy, and cement, specifically a pneumatic transmission device for a fan outlet check valve. Background Technology

[0002] In flue gas systems of power plants, metallurgy, cement, and other industries, the non-return valve at the fan outlet is a critical piece of equipment, playing a vital role in preventing backflow of the medium and ensuring the safe operation of the system. This is especially true in applications at the outlets of induced draft fans and forced draft fans in large-capacity units of 600MW and above, where its operational reliability directly affects the stable operating conditions of the unit. The flue gas ducts of such units are typically large in size (e.g., the flue gas duct at the outlet of the induced draft fan can reach 6000×6000mm). The non-return valves often adopt a double-leaf, swing-out structure, with the door panel connected to the door frame via a rotating shaft. The opening and closing action is achieved by a drive device that allows for 0-90° rotation.

[0003] Currently, the mainstream method for driving the non-return valve at the fan outlet in the industry is pneumatic drive. In the traditional structure, the drive cylinder is directly connected to and pushes the crank arms installed on the rotary shafts on both sides of the non-return valve. The crank arms drive the rotary shafts to rotate, thereby opening and closing the valve. This transmission method can work normally when the non-return valve has no back pressure, but it has significant limitations during unit operation: when a single-sided fan fails and is undergoing online maintenance, the non-return valve needs to be opened with the back pressure of flue gas when the fan is started. At this time, there is a pressure difference of up to 4.5 kPa in the flue, which causes the opening resistance of the valve to increase sharply, resulting in a significant increase in the opening resistance torque (taking a non-return valve in a 6000×6000mm flue as an example, the instantaneous opening resistance torque on each side is about 55 kNm).

[0004] Existing commercially available linear pneumatic cylinders, limited by their structural design, can only achieve a maximum output torque of 20 kNm (e.g., a non-customized linear cylinder with a cylinder diameter of Φ350 mm). Even if the check valve is split into multiple drive units, it still cannot meet the drive torque required for opening with back pressure, resulting in the check valve failing to open normally and affecting the efficiency of unit recovery after maintenance. To solve this problem, the industry has tried using high-torque electric actuators, but such mechanisms are costly and lack the emergency operation flexibility of pneumatic drives (e.g., emergency opening by opening the air circuit in case of pneumatic system failure), making it difficult to meet the dual requirements of power plants for equipment economy and safety.

[0005] Therefore, how to improve the driving torque by optimizing the transmission method while retaining the advantages of pneumatic drive, and solve the problem of opening large-size flue gas duct check valves with back pressure, has become a technical bottleneck that urgently needs to be overcome in the current upgrade of fan outlet check valve equipment. Utility Model Content

[0006] The purpose of this invention is to provide a pneumatic transmission device for a fan outlet check valve, which solves the above-mentioned technical problems.

[0007] To achieve the above objectives, this utility model provides the following technical solution: a pneumatic transmission device for a fan outlet anti-return valve, comprising an anti-return valve body, a primary transmission mechanism, a secondary transmission mechanism, a pneumatic drive assembly, and a pneumatic control cabinet. The anti-return valve body is adapted to the large-size flue gas duct at the outlet of a 600MW or higher unit fan. It adopts a two-layer combined structure, with each layer being a double-leaf swing-out door panel. Door bolts are fixedly installed on the edges of the door panels. The two sides of the door panels are rotatably connected to the door frame through door panel rotation shafts and door panel hinges. When the door panels are closed, they are sealed and fitted tightly against the door frame.

[0008] The pneumatic drive assembly is mounted on the left and right side bases fixed to the top of the pipe. The bases are fixed to the pipe flange by welding. The pneumatic drive assembly includes at least two sets of linear drive cylinders. The bottom of the drive cylinder is fixed by a cylinder support. The piston rod end of the drive cylinder is equipped with a spherical bearing and is connected to the primary transmission mechanism by a pin.

[0009] The primary transmission mechanism consists of a primary rotary shaft, a crank arm, and a support bearing. The primary rotary shaft is horizontally installed on the top of the pipe via the support bearing. One end of the crank arm is fixed to the primary rotary shaft via a flat key, and the other end is hinged to the piston rod of the drive cylinder via a spherical bearing.

[0010] The secondary transmission mechanism includes a secondary rotary shaft, a drive arm, a drive swing arm, and a drive roller. The secondary rotary shaft is installed on the top of the pipe through bearings and a sealing seat. One end of the shaft is inserted into the pipe and fixed vertically to the drive arm. The other end is connected to the primary rotary shaft through a coupling. The drive arm extends along the width of the pipe and is connected to the drive roller at its end through the drive swing arm. The drive roller makes rolling contact with the door bolt of the door panel.

[0011] The pneumatic control cabinet is connected to the drive cylinder through a pneumatic pipeline and integrates pneumatic control elements and control circuits, which can realize the "right door closed / left door closed" and "right door open / left door open" status control of the double-leaf door panel.

[0012] Preferably, the crank arm is forged from alloy steel and has a length of 500-600mm. The connection between the crank arm and the first-stage rotary shaft is reinforced with ribs, the thickness of which is 20-25mm. The hinge joint between the crank arm and the piston rod is fitted with a canvas dust cover, and both ends are fixed with clamps. The first-stage rotary shaft is made of No. 45 steel with a heat treatment, a shaft diameter of 80-100mm, and is chrome-plated to enhance wear resistance. The support bearing is a deep groove ball bearing.

[0013] Preferably, the sealing seat of the secondary rotary shaft includes a fixed flange, a stuffing box, and a gland. The fixed flange is welded to the mounting hole at the top of the pipe. The stuffing box is filled with 4-6 layers of flexible graphite packing. The gland is sealed by compressing the packing with bolts. The drive arm is made of seamless steel pipe with an outer diameter of 60-80mm and a wall thickness of 8-10mm.

[0014] Preferably, the drive roller is made of nylon with an outer diameter of 100-120mm and an inner ring equipped with a sealed rolling bearing, which can rotate flexibly around the pin; the door bolt is made of round steel with a diameter of 50-60mm, with a polished surface, and is connected to the door panel by double-sided welding with a weld leg height of 15-20mm.

[0015] Preferably, the pneumatic control cabinet integrates a pressure regulating valve, a filter, an oil mist lubricator, and a solenoid valve assembly. The pressure regulating valve can adjust the inlet pressure to 0.6-0.8MPa, the filter has a filtration accuracy of 5μm, and the oil mist lubricator adds lubricating oil to the compressed air. The solenoid valve assembly uses dual electrically controlled solenoid valves, which correspond to the drive cylinders of the double-leaf door panels. The cabinet surface is equipped with "Right Door Closed", "Left Door Closed", "Right Door Opened", and "Left Door Opened" operation buttons and status indicator lights.

[0016] Preferably, the door panel of the non-return valve body is made of Q345R steel plate with a thickness of 16-20mm. The edge of the door panel is provided with nitrile rubber sealing strips, which are fixed in the sealing groove by bolts. The door frame is made of welded steel profiles, and the connection part with the pipe flange is provided with a positioning pin with a diameter of 20-25mm. The inner side of the door frame is provided with a 15-20° guide slope.

[0017] Preferably, the pneumatic drive components of the upper and lower check valves are connected in parallel to the same pneumatic control cabinet through pneumatic pipeline 51, and the cabinet is equipped with branch solenoid valves.

[0018] Preferably, the device also includes a limit detection component, which consists of a limit switch and a sensor. The limit switch is installed on the base corresponding to the "open" and "close" positions of the primary rotary shaft, respectively. The sensor is fixed on the primary rotary shaft. When the rotary shaft rotates to the corresponding position, the sensor triggers the limit switch, and the signal is transmitted to the pneumatic control cabinet to cut off the gas circuit. The device also includes a process column, which is welded to the middle position inside the door frame.

[0019] This utility model provides a pneumatic transmission device for a fan outlet check valve. It has the following beneficial effects:

[0020] 1. This utility model utilizes a composite structure of "first-stage rotary transmission + second-stage long arm drive" to significantly amplify the pneumatic drive torque by lever principle, completely solving the problem of opening large-size flue check valves with back pressure. In traditional devices, the drive cylinder directly pushes the door panel rotary shaft crank arm. Limited by the cylinder output torque, it cannot cope with the 55KNm opening resistance torque of a 6000×6000mm flue check valve with back pressure. In this device, the drive cylinder of the pneumatic drive component first transmits the force to the first-stage rotary shaft through the first-stage transmission mechanism—the piston rod extends and retracts, causing the crank arm to swing, driving the first-stage rotary shaft to rotate, completing the conversion from linear stroke to rotary motion. The first-stage rotary shaft drives the second-stage rotary shaft of the second-stage transmission mechanism to rotate synchronously through a coupling, causing the drive long arm inside the pipe to rotate along the width direction. The drive roller at the end of the drive long arm pushes the door panel open through the door bolt.

[0021] 2. This two-stage transmission structure amplifies the driving torque by 3-4 times by extending the lever arm (the length of the drive arm is adapted to the width of the flue), enabling a Φ350mm cylinder to output a torque of 60-80KNm, easily handling the opening requirements under a maximum back pressure of 4.5KPa. Simultaneously, the crank arm is forged from alloy steel with reinforcing ribs, the first-stage rotary shaft is heat-treated and chrome-plated, and the support bearings are deep groove ball bearings, ensuring structural strength and wear resistance under high torque transmission. The device has a continuous operating life exceeding 100,000 switching cycles, and its reliability is 60% higher than traditional direct drive systems.

[0022] 3. This utility model adopts a modular architecture of "layered combination + independent control" and a refined pneumatic control system to adapt to different sizes of flue gas ducts and operating scenarios, significantly reducing installation and maintenance costs. For ultra-wide flue gas ducts, the check valve body adopts a two-layer combined structure, with each layer featuring a double-leaf opening design. The pneumatic drive components of each layer are connected in parallel to the same pneumatic control cabinet through air ducts. The branch solenoid valves in the cabinet can achieve independent control of a single layer or synchronous control of two layers. During synchronization, the flow control valve ensures that the opening speed difference between the two door panels is ≤0.5s / 90°, adapting to the installation requirements of ducts of different widths. At the control level, the pneumatic control cabinet integrates a pressure regulating valve, a 5μm precision filter, and a dual-electro-controlled solenoid valve group, supporting independent operation of "right door closed / left door closed" and "right door open / left door open". The cabinet status indicator lights provide real-time feedback on the door panel position. The limit detection component accurately captures the "open / closed" signal through a limit switch and a sensor, automatically cutting off the air path after triggering the limit switch to prevent damage to the equipment due to overtravel. Attached Figure Description

[0023] Figure 1 This is a perspective view of the overall structure of this utility model;

[0024] Figure 2 This is a front view of the overall structure of this utility model;

[0025] Figure 3This utility model Figure 2 DD section view;

[0026] Figure 4 This is a top view of the overall structure of this utility model;

[0027] Figure 5 This is the control logic diagram of the pneumatic control cabinet of this utility model.

[0028] In the diagram: door panel 1, door panel rotating shaft 11, door frame 12, door panel hinge 13, process column 14, drive cylinder 21, cylinder support 22, primary rotating shaft 31, crank arm 32, support bearing 33, secondary rotating shaft 41, drive long arm 42, drive swing arm 43, drive roller 44, sealing seat 45, pneumatic control cabinet 5, and pneumatic pipeline 51. Detailed Implementation

[0029] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0030] Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0031] Example 1:

[0032] A preferred embodiment of the pneumatic transmission device for a fan outlet check valve provided by this utility model is, for example... Figure 1-5 As shown: A pneumatic transmission device for a non-return valve at a fan outlet includes a non-return valve body, a primary transmission mechanism, a secondary transmission mechanism, a pneumatic drive assembly, and a pneumatic control cabinet 5. The non-return valve body is adapted to the large-size flue gas duct at the fan outlet of a 600MW or larger unit. It can adopt a two-layer combined structure (a single layer is adapted to a duct with a width of 4000-4300mm). Each layer is a double-leaf swing-open door panel 1. Door bolts are fixedly installed on the edge of the door panel 1. The two sides of the door panel 1 are rotatably connected to the door frame 12 through the door panel rotation shaft 11 and the door panel hinge 13. When the door panel 1 is closed, it is sealed and fitted with the door frame 12, and can withstand a flue gas back pressure of 4.5KPa or higher.

[0033] The pneumatic drive assembly is mounted on the left and right side bases fixed to the top of the pipe. The bases are fixed to the pipe flange by welding. The pneumatic drive assembly includes at least two sets of linear drive cylinders 21. The cylinder diameter is Φ350mm. The bottom of the drive cylinder 21 is fixed by the cylinder support 22. The piston rod end of the drive cylinder 21 is equipped with a spherical bearing and is connected to the primary transmission mechanism by a pin.

[0034] The primary transmission mechanism consists of a primary rotary shaft 31, a crank arm 32, and a support bearing 33. The primary rotary shaft 31 is horizontally installed on the top of the pipe via the support bearing 33. One end of the crank arm 32 is fixed to the primary rotary shaft 31 via a flat key, and the other end is hinged to the piston rod of the drive cylinder 21 via a spherical bearing. When the cylinder extends or retracts, it drives the crank arm 32 to drive the primary rotary shaft 31 to complete a 0-90° rotational motion.

[0035] The secondary transmission mechanism includes a secondary rotary shaft 41, a drive arm 42, a drive swing arm 43, and a drive roller 44. The secondary rotary shaft 41 is installed on the top of the pipe through a bearing and a sealing seat 45. One end of the shaft is inserted into the pipe and fixed vertically to the drive arm 42. The other end is connected to the primary rotary shaft 31 through a coupling. The drive arm 42 extends along the width of the pipe and is connected to the drive roller 44 at its end through the drive swing arm 43. The drive roller 44 makes rolling contact with the bolt of the door panel 1.

[0036] The pneumatic control cabinet 5 is connected to the drive cylinder 21 through the pneumatic pipeline 51, and integrates pneumatic control elements and control circuits to realize the "right door closed / left door closed" and "right door open / left door open" status control of the double door panel 1. When the pneumatic drive component is activated, the primary rotary shaft 31 drives the secondary rotary shaft 41 to rotate, and the drive arm 42 pushes the door bolt through the drive roller 44, so that the door panel 1 can realize the 0-90° opening and closing action around the door panel 1 rotary shaft. The cylinder driving force is amplified through the lever principle to ensure that the non-return door opens with back pressure.

[0037] The crank arm 32 is forged from alloy steel and has a length of 500-600mm. The connection between the crank arm 32 and the first-stage rotary shaft 31 is reinforced with ribs, which are 20-25mm thick, to improve bending strength. The hinge between the crank arm 32 and the piston rod is fitted with a canvas dust cover, which is fixed at both ends with clamps to prevent impurities from entering the joint bearing. The first-stage rotary shaft 31 is made of 45# steel with a heat treatment process and a shaft diameter of 80-100mm. The surface is chrome-plated to enhance wear resistance. The support bearing 33 is a deep groove ball bearing to ensure that the coaxiality error of the rotary shaft rotation is ≤0.5mm.

[0038] The sealing seat 45 of the secondary rotary shaft 41 includes a fixed flange, a stuffing box, and a gland. The fixed flange is welded to the mounting hole at the top of the pipe. The stuffing box is filled with 4-6 layers of flexible graphite packing. The gland is sealed by compressing the packing with bolts. It can withstand a pressure difference of 0-10 kPa without leakage. The drive arm 42 is made of seamless steel pipe with an outer diameter of 60-80 mm and a wall thickness of 8-10 mm. The drive swing arm 43 is connected to the drive arm 42 by a pin. The angle can be finely adjusted around the pin to adapt to the position changes during the opening and closing of the door panel 1.

[0039] The drive roller 44 is made of nylon with an outer diameter of 100-120mm. The inner ring is equipped with a sealed rolling bearing, which can rotate flexibly around the pin. The door bolt is made of round steel with a diameter of 50-60mm and the surface is polished. It is connected to the door panel 1 by double-sided welding with a weld leg height of 15-20mm to ensure that the connection strength is sufficient to withstand the thrust of the drive roller 44.

[0040] The pneumatic control cabinet 5 integrates a pressure regulating valve, filter, lubricator, and solenoid valve assembly. The pressure regulating valve can adjust the inlet pressure to 0.6-0.8MPa, the filter has a filtration accuracy of 5μm, and the lubricator adds lubricating oil to the compressed air. The solenoid valve assembly adopts dual electrically controlled solenoid valves, which correspond to the drive cylinders of the double-leaf door panel 1. The cabinet surface is equipped with "Right door closed", "Left door closed", "Right door open", and "Left door open" operation buttons and status indicator lights, which can realize independent control of single or double-leaf door panels 1.

[0041] The door panel 1 of the non-return valve body is made of Q345R steel plate with a thickness of 16-20mm. The edge of the door panel 1 is equipped with nitrile rubber sealing strips, which are fixed in the sealing groove by bolts. The door frame 12 is welded from steel profiles. The connection with the pipe flange is equipped with a positioning pin with a diameter of 20-25mm. The inner side of the door frame 12 is equipped with a 15-20° guide slope to guide the door panel 1 to close accurately. The leakage rate is ≤0.5% / h when closed.

[0042] The pneumatic drive components of the upper and lower non-return valves are connected in parallel to the same pneumatic control cabinet 5 through the air pipeline (51). The cabinet is equipped with a branch solenoid valve, which can realize the individual control or synchronous control of the two non-return valves. During synchronous control, the air intake speed of the cylinder is adjusted by the flow control valve with an adjustment accuracy of 0.1L / min to ensure that the opening / closing speed difference between the two door panels 1 is ≤0.5s / 90°.

[0043] Example 2:

[0044] Please see Figures 1-5Furthermore, based on Embodiment 1, the following is further provided: It also includes a limit detection component, which consists of a limit switch and a sensing element. The limit switches are respectively installed on the bases corresponding to the "open" and "closed" positions of the primary rotary shaft 31. The sensing element is fixed on the primary rotary shaft 31. When the rotary shaft rotates to the corresponding position, the sensing element triggers the limit switch, and the signal is transmitted to the pneumatic control cabinet 5 to cut off the gas path. The limit switch has an IP65 protection rating, adapting to the harsh environment of the flue gas duct. The device also includes a process column 14, which is welded to the middle position inside the door frame 12 for pipeline installation and equipment support.

[0045] When the system is in use and maintenance is completed, if the non-return valve needs to be opened, the corresponding side drive cylinder 21 is started by operating the button on the pneumatic control cabinet 5. Compressed air is delivered to the cylinder through the air pipeline 51, the pressure regulating valve adjusts the pressure to 0.6-0.8MPa, the filter filters impurities, and the oil mist lubricator adds lubricating oil to ensure smooth operation of the cylinder.

[0046] The piston rod of the drive cylinder extends and retracts, which drives the crank arm 32 of the first-stage transmission mechanism to swing through the end joint bearing. The crank arm drives the first-stage rotary shaft 31 to rotate around the support bearing 33 via the flat key, completing the conversion from pneumatic linear stroke to rotary motion. At this time, the induction plate rotates synchronously with the first-stage rotary shaft.

[0047] The primary rotary shaft 31 drives the secondary rotary shaft 41 of the secondary transmission mechanism to rotate through the coupling. The secondary rotary shaft passes through the sealing seat 45 and enters the inside of the pipe. The drive arm 42, which is vertically fixed at its end, rotates synchronously with the shaft.

[0048] The drive arm swings along the width of the flue, and the drive swing arm 43 at the end drives the drive roller 44 made of nylon to roll. The drive roller contacts the door bolt at the edge of the door panel 1 and applies a pushing force. The door panel rotates around the door panel rotation axis 11 and the door panel hinge 13 to achieve a 0-90° opening action. The 15-20° guide slope on the inner side of the door frame 12 guides the door panel to be accurately aligned. When closed, the nitrile rubber sealing strip achieves a seal.

[0049] When the primary rotary shaft 31 rotates to the "open position", the sensor plate fixed on the shaft triggers the limit switch, and the signal is transmitted to the pneumatic control cabinet 5. The control system cuts off the air circuit, drives the cylinder to stop, and keeps the door open. The closing process is the same. The machine stops after the sensor plate touches the "closed position" limit switch.

[0050] If a specific door panel needs to be controlled individually, the "right door open / left door open" operation can be achieved independently through the branch solenoid valve of the pneumatic control cabinet; the upper and lower non-return doors can be controlled synchronously or in layers to adapt to different operating conditions.

[0051] Finally, it should be noted that the above description is merely a preferred embodiment of this utility model and is not intended to limit the utility model. Although the utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

Claims

1. A pneumatic drive for a fan outlet check door, characterized by, It includes a non-return door body, a primary transmission mechanism, a secondary transmission mechanism, a pneumatic drive assembly and a pneumatic control cabinet (5). The non-return door body is adapted to the large-size flue gas duct at the outlet of the fan of a 600MW or above unit. It adopts a two-layer combined structure, each layer is a double-leaf swing door panel (1). Door bolts are fixedly installed on the edge of the door panel (1). The two sides of the door panel (1) are rotatably connected to the door frame (12) through the door panel rotation shaft (11) and the door panel hinge (13). When the door panel (1) is closed, it is sealed and fitted with the door frame (12). The pneumatic drive assembly is mounted on the left and right side bases fixed to the top of the pipe. The bases are fixed to the pipe flange by welding. The pneumatic drive assembly includes at least two sets of linear drive cylinders (21). The bottom of the drive cylinder (21) is fixed by a cylinder support (22). The piston rod end of the drive cylinder (21) is equipped with a spherical bearing and is connected to the primary transmission mechanism by a pin. The primary transmission mechanism consists of a primary rotating shaft (31), a crank arm (32), and a support bearing (33). The primary rotating shaft (31) is horizontally installed on the top of the pipe via the support bearing (33). One end of the crank arm (32) is fixed to the primary rotating shaft (31) via a flat key, and the other end is hinged to the piston rod of the drive cylinder (21) via a spherical bearing. The secondary transmission mechanism includes a secondary rotary shaft (41), a drive arm (42), a drive swing arm (43), and a drive roller (44). The secondary rotary shaft (41) is installed on the top of the pipe through a bearing and a sealing seat (45). One end of the shaft is inserted into the pipe and fixed vertically to the drive arm (42). The other end is connected to the primary rotary shaft (31) through a coupling. The drive arm (42) extends along the width of the pipe, and the end is connected to the drive roller (44) through the drive swing arm (43). The drive roller (44) makes rolling contact with the bolt of the door panel (1). The pneumatic control cabinet (5) is connected to the drive cylinder (21) through the pneumatic pipeline (51), and integrates pneumatic control elements and control circuits, which can realize the "right door closed / left door closed" and "right door open / left door open" status control of the double door panel (1).

2. The air drive for a fan outlet check door according to claim 1, wherein, The crank arm (32) is forged from alloy steel and has a length of 500-600mm. The connection between the crank arm (32) and the first-stage rotary shaft (31) is reinforced with a thickness of 20-25mm. The hinge of the crank arm (32) and the piston rod is fitted with a dust cover made of canvas and fixed at both ends by clamps. The first-stage rotary shaft (31) is made of No. 45 steel with a diameter of 80-100mm and is chrome-plated to enhance wear resistance. The support bearing (33) is a deep groove ball bearing.

3. The air drive for a fan outlet check door according to claim 1, wherein, The sealing seat (45) of the secondary rotary shaft (41) includes a fixed flange, a stuffing box and a gland. The fixed flange is welded to the mounting hole at the top of the pipe. The stuffing box is filled with 4-6 layers of flexible graphite packing. The gland is sealed by compressing the packing with bolts. The drive arm (42) is made of seamless steel pipe with an outer diameter of 60-80mm and a wall thickness of 8-10mm.

4. The air drive for a fan outlet check door according to claim 1, wherein, The drive roller (44) is made of nylon with an outer diameter of 100-120mm. The inner ring is equipped with a sealed rolling bearing and can rotate flexibly around the pin. The door bolt is made of round steel with a diameter of 50-60mm and the surface is polished. It is connected to the door panel (1) by double-sided welding with a weld leg height of 15-20mm.

5. The air drive for a fan outlet check door according to claim 1, wherein, The pneumatic control cabinet (5) integrates a pressure regulating valve, a filter, an oil mist lubricator, and a solenoid valve assembly. The pressure regulating valve can adjust the inlet pressure to 0.6-0.8MPa, the filter has a filtration accuracy of 5μm, and the oil mist lubricator adds lubricating oil to the compressed air. The solenoid valve assembly adopts a dual-electric control solenoid valve, which corresponds to the drive cylinder of the double-leaf door panel (1). The cabinet surface is equipped with "Right door closed", "Left door closed", "Right door open" and "Left door open" operation buttons and status indicator lights.

6. The air drive for a damper door of a fan as set forth in claim 1, wherein The door panel (1) of the non-return valve body is made of Q345R steel plate with a thickness of 16-20mm. The edge of the door panel (1) is provided with nitrile rubber sealing strips, which are fixed in the sealing groove by bolts. The door frame (12) is made of welded steel profiles. The connection part with the pipe flange is provided with a positioning pin with a diameter of 20-25mm. The inner side of the door frame (12) is provided with a 15-20° guide slope.

7. The air-actuated drive for a fan outlet check door according to claim 1, wherein, The pneumatic drive components of the upper and lower non-return valves are connected in parallel to the same pneumatic control cabinet (5) through pneumatic pipelines (51), and the cabinet is equipped with branch solenoid valves.

8. The air drive for a damper door according to any one of claims 1 to 7, wherein It also includes a limit detection component, which consists of a limit switch and a sensor plate. The limit switch is installed on the base corresponding to the "open" and "closed" positions of the primary rotary shaft (31). The sensor plate is fixed on the primary rotary shaft (31). When the rotary shaft rotates to the corresponding position, the sensor plate triggers the limit switch, and the signal is transmitted to the pneumatic control cabinet (5) to cut off the air circuit. The device also includes a process column (14), which is welded to the middle position inside the door frame (12).

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