Swing check valve

Abstract

The invention belongs to the technical field of valves, and particularly relates to a swing check valve which comprises a valve body, a rotating part is rotationally assembled on the valve body through a rotating assembly, a valve clack assembly is rotationally assembled in the rotating part through a fixing disc, the valve clack assembly can adjust the limiting direction of the flow direction of a medium according to needs, and the swing check valve further comprises a limiting assembly used for limiting the rotating part. The valve clack assembly comprises a connecting rod, the connecting rod is rotationally assembled on one side of the fixing disc, a valve clack is fixedly assembled on the connecting rod through a fixing bolt, and a damping mechanism for providing damping for the valve clack assembly is arranged on the fixing disc. Compared with the prior art, the check valve has the advantages that the material cost is reduced, the occupied space of equipment is reduced, the adjustment process is convenient, the maintenance cost is reduced, the check valve has higher flexibility and expandability, the production efficiency of enterprises is also improved, and meanwhile the reliability of a pipeline system is greatly improved due to the arrangement of the damping mechanism.

Description

Technical Field

[0001] The invention belongs to the technical field of valves, in particular to a swing check valve. Background Art

[0002] A check valve, also known as a non-return valve or a one-way valve, ensures that the fluid can only flow in one direction to prevent backflow. Its working principle is based on the automatic opening and closing of the valve disc. A swing check valve is one of them. It is opened or closed by rotating the valve disc around the shaft to prevent the medium from flowing back. Its characteristics include small flow resistance, easy opening and closing, and corrosion resistance. It is suitable for a variety of media and occasions. It is widely used in petroleum, chemical, food, construction, and water supply and drainage systems to prevent the medium from flowing back and protect equipment.

[0003] The existing swing check valve is mainly composed of the following parts: valve body, valve cover, valve disc, sealing ring, etc. The working principle is: when the fluid flows forward, the valve disc is squeezed and rotated open by the fluid pressure; when the fluid stops or flows back, the valve disc rotates and closes due to its own weight or spring force to prevent backflow.

[0004] The swing check valve in the existing technology has the following disadvantages: in the chemical production process, the process flow will be adjusted according to different product requirements and production stages, and the flow direction of the fluid also needs to be changed accordingly, which usually requires the addition of external pipelines to achieve this. This not only increases the material cost, but also takes up more equipment space, making the entire chemical production system more complex and large, and extremely inconvenient to operate. In addition, if the worker installs it in the wrong direction during installation, the check direction needs to be disassembled and reinstalled, which is a cumbersome process, consuming time and manpower, increasing maintenance costs, lacking flexibility, and the check direction is fixed, which cannot meet the complex and changeable fluid flow requirements, limiting the flexibility and scalability of the system. At the same time, the installation cost of the production enterprise is high. If the adjustment of the check direction is not considered when designing the pipeline system, later adjustments may require large-scale transformation of the pipeline system, increasing costs and engineering difficulty, and affecting production efficiency. Therefore, a swing check valve is proposed to address the above problems. Summary of the invention

[0005] In order to make up for the shortcomings of the existing swing check valve, the present invention is easy to operate, and the check direction can be adjusted without disassembly and reinstallation, and without adding external pipelines, thereby saving manpower and time, enhancing system flexibility, adapting to different process flows and production requirements, saving materials and space, reducing costs, making the system more compact, and improving production efficiency. A swing check valve is proposed.

[0006] The technical solution adopted by the present invention to solve its technical problem is: a swing check valve described in the present invention includes a valve body, wherein the two ends of the valve body are respectively a first liquid port and a second liquid port, and the valve body is rotatably equipped with a rotating part that can be adjusted in angle relative to the valve body through a rotating component, and the rotating part is fixedly equipped with an upper cover, and the rotating part is internally equipped with a valve flap assembly on a fixed disk through a rotating column, and the fixed disk is provided with an adjustment mechanism for switching the valve flap assembly between an adjustment mode and an unadjusted mode, and the valve body is provided with an adjustment area for the valve flap assembly to rotate, and the valve flap assembly can adjust the limiting direction of the medium flow direction as needed, and also includes a limit assembly for limiting the rotating part.

[0007] Preferably, the rotating assembly includes a rotating sleeve, and an upper flange rotatably arranged thereon and a lower flange thereunder, and the upper flange and the lower flange are fixedly connected to the rotating part and the valve body respectively by fixing bolts.

[0008] Preferably, the limit assembly includes a shell, a movable block is slidably arranged in the shell through a tension spring, a button is arranged at one end of the movable block, a locking pin is movably arranged in the shell, one end of the locking pin extends to the outside of the shell, a locking groove cooperating with the locking pin is provided on the upper flange, and a driving surface for the locking pin to move and open and close is provided on the movable block.

[0009] Preferably, the adjustment mechanism includes an adjusting nut fixedly arranged at one end of a rotating column, a locking column slidingly passing through the adjusting nut, and a positioning groove provided on one side of a fixed disk and corresponding to the locking column, an adjusting block for opening and closing the locking column is provided at one end of the locking column through rotation of a rotating shaft, and a reset spring for resetting the locking column is terminated between the other end of the locking column and the adjusting nut.

[0010] Preferably, the tension spring is used to drive the moving block so that the driving surface inserts the locking pin into the locking groove.

[0011] Preferably, a pulley is rotatably provided on the end of the locking pin opposite to the driving surface.

[0012] Preferably, the valve flap assembly includes a connecting rod, which is rotatably mounted on one side of a fixed disk, and the valve flap is fixedly mounted on the connecting rod via a fixing bolt, and a damping mechanism for providing damping to the valve flap assembly is provided on the fixed disk.

[0013] Preferably, the fixed plate is composed of a first fixing ring and a second fixing ring assembled and fixed, the damping mechanism includes a first cavity and a second cavity respectively opened on opposite surfaces of the first fixing ring and the second fixing ring, and sealing baffles for sealing the first cavity and the second cavity are fixedly assembled on opposite surfaces of the first fixing ring and the second fixing ring, sealing rings for improving the sealing are arranged on both sides of the sealing baffle, a plurality of through holes for connecting the first cavity and the second cavity are arranged on the sealing baffle, a piston assembly is slidably arranged in the second cavity, the piston assembly is linked to the connecting rod, and when the valve disc is opened, the piston assembly presses the air in the second cavity into the first cavity through the through hole.

[0014] Preferably, when the valve flap is closed, the piston assembly is located at the beginning of the stroke in the second cavity, and several through holes are exposed; when the valve flap is opened, the piston assembly moves toward the end of the stroke in the second cavity, and several through holes are gradually blocked by the piston assembly.

[0015] Preferably, a sealing plug corresponding to the valve seat at the flow channel on the valve body is fixedly provided on one side of the valve disc.

[0016] Preferably, a soft cushion is fixedly provided on one side of the valve flap for preventing the valve flap from colliding with the valve body.

[0017] Beneficial effects of the present invention:

[0018] 1. The present invention provides a swing check valve, which enables the fluid check direction of the check valve to be changed accordingly according to production needs, without relying on adding external pipelines to achieve, thereby reducing material costs, reducing the space occupied by equipment, facilitating the adjustment process, reducing maintenance costs, making the check valve more flexible and scalable, and also improving the production efficiency of the enterprise;

[0019] 2. Through the setting of the damping mechanism, a progressive damping change is achieved. This design can provide appropriate damping according to different stages of movement, making the movement smoother and more controllable. When the fluid pressure is unbalanced, it prevents the valve disc from swinging up and down significantly, effectively preventing the valve disc from excessive wear. At the same time, it solves the vibration and noise of the pipeline system caused by the swing of the valve disc, and prevents the turbulence and eddy current of the fluid caused by the unstable state of the valve disc swinging significantly, prevents the loss of pipeline transportation energy, improves the fluid transportation efficiency, effectively prevents safety problems such as water hammer from causing huge impact on the pipeline system, and greatly improves the reliability of the pipeline system. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of this application. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0021] Figure 1 It is a cross-sectional view of the internal structure when the check valve is closed;

[0022] Figure 2 It is a cross-sectional view of the internal structure when the check valve is open;

[0023] Figure 3 It is a cross-sectional view of the internal structure of the check valve when it is opened after the check direction is adjusted;

[0024] Figure 4 It is a top view of the cross section of the valve body at the fixed disc position;

[0025] Figure 5 It is a cross-sectional view of the fixed plate and the second cavity and a schematic diagram of the position of the piston assembly when the valve disc is closed;

[0026] Figure 6 It is a cross-sectional view of the fixed plate and the second cavity and a schematic diagram of the position of the piston assembly when the valve disc is open;

[0027] Figure 7 is a cross-sectional view of the fixed disk, the first cavity, the second cavity, and the adjustment mechanism;

[0028] Figure 8 yes Figure 6 A magnified view of the structure at center A;

[0029] Fig. 9 is a cross-sectional view of the rotating assembly;

[0030] Fig.10 yes Figure 8 The enlarged structure diagram at A in the middle;

[0031] Fig.11 is a structural schematic diagram of the first cavity and the sealing ring;

[0032] Fig.12 is a schematic structural diagram of a second fixing ring;

[0033] Legend:

[0034] 1. Valve body; 01. First liquid port; 02. Second liquid port; 101. Adjustment area; 102. Valve seat; 2. Rotating assembly; 201. Rotating sleeve; 202. Upper flange; 203. Lower flange; 3. Rotating part; 4. Upper cover; 5. Valve flap assembly; 501. Connecting rod; 5011. Connecting rod; 502. Valve flap; 5021. Sealing plug; 5022. Cushion; 6. Limiting assembly; 601. Housing; 602. Tension spring; 603. Moving block; 6031. Driving surface; 604. Button; 605 , locking pin; 606, locking groove; 7, fixing plate; 700, rotating column; 701, first fixing ring; 702, second fixing ring; 8, damping mechanism; 801, first cavity; 802, second cavity; 8021, piston assembly; 80211, piston seat; 80212, sealing piston; 803, sealing baffle; 8031, through hole; 8032, sealing ring; 9, adjusting mechanism; 900, adjusting nut; 901, locking column; 902, positioning groove; 903, adjusting block; 904, return spring. DETAILED DESCRIPTION

[0035] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] Specific examples are given below.

[0037] See also Figure 1-Figure 12 The present invention discloses a swing check valve, comprising a valve body 1, wherein the two ends of the valve body 1 are respectively a first liquid port 01 and a second liquid port 02, wherein the valve body 1 is rotatably equipped with a rotating portion 3 capable of adjusting the angle relative to the valve body 1 through a rotating assembly 2, wherein an upper cover 4 is fixedly equipped on the rotating portion 3, wherein a valve flap assembly 5 is rotatably equipped on a fixed disk 7 in the rotating portion 3 through a rotating column 700, wherein an adjusting mechanism 9 for switching the valve flap assembly 5 between an adjustment mode and an unadjusted mode is arranged on the fixed disk 7, and wherein the valve body 1 has a plurality of holes for the valve flap assembly 5 to rotate. The valve flap assembly 5 can adjust the limiting direction of the medium flow direction as needed, and also includes a limit assembly 6 for limiting the rotating part 3. The rotating assembly 2 includes a rotating sleeve 201, and an upper flange 202 rotatably arranged thereon and a lower flange 203 below, and the upper flange 202 and the lower flange 203 are respectively fixedly connected to the rotating part 3 and the valve body 1 through fixing bolts. The valve flap assembly 5 includes a connecting rod 501, and the connecting rod 501 is rotatably assembled on one side of the fixed disk 7, and the valve flap 502 is fixedly assembled on the connecting rod 501 through fixing bolts;

[0038] The limit assembly 6 includes a shell 601, a moving block 603 is slidably arranged in the shell 601 through a tension spring 602, a button 604 is arranged at one end of the moving block 603, a locking pin 605 is movably arranged in the shell 601, one end of the locking pin 605 extends to the outside of the shell 601, a locking groove 606 cooperating with the locking pin 605 is provided on the upper flange 202, a driving surface 6031 for the locking pin 605 to move and open and close is provided on the moving block 603, and the tension spring 602 is used to drive the moving block 603 so that the driving surface 6031 inserts the locking pin 605 into the locking groove 606 The end of the lock pin 605 opposite to the driving surface 6031 is rotatably provided with a pulley 6051, the adjustment mechanism 9 includes an adjustment nut 900 fixedly provided at one end of the rotating column 700, a lock column 901 is slidably penetrated on the adjustment nut 900, and also includes a positioning groove 902 provided on one side of the fixed plate 7 and correspondingly matched with the lock column 901, an adjustment block 903 for opening and closing the lock column 901 is rotatably provided at one end of the lock column 901 through a rotating shaft, and a reset spring 904 for resetting the lock column 901 is terminated between the other end of the lock column 901 and the adjustment nut 900;During operation, in order to enable the check valve to change the restricting direction of the fluid in the pipeline according to different production processes and requirements and meet the complex and changeable fluid flow requirements, first when the staff needs to adjust the check direction of the check valve, it is necessary to unlock the limit assembly 6 and press the button 604. The button 604 drives the moving block 603 to move, and the tension spring 602 is stretched. The moving block 603 moves and drives the driving surface 6031 to move. The locking pin 605 moves along the slope of the driving surface 6031 under the action of gravity. When the locking pin 605 falls, the locking pin 605 leaves the locking slot 606, and the button 604 is released. Then, the valve flap assembly 5 needs to be adjusted to the adjustment mode through the adjustment mechanism 9. The staff rotates the adjustment nut 900, and the adjustment nut 900 drives the rotating column 700 and the valve flap assembly 5 to rotate. When the locking column 901 rotates to a position where it can be inserted into the positioning slot 902, the staff pulls the adjustment block 903. At this time, the locking column 901 is inserted into the positioning slot 902 under the elastic potential energy of the return spring 904, limiting the angle of the valve flap assembly 5, thereby making the valve flap assembly 5 The rotation can be completed normally at the adjustment area 101 in the valve body 1. At this time, the rotating part 3 is rotated, and the valve disc assembly 5 inside it is rotated to the opposite direction. When the valve disc assembly 5 rotates 180 degrees, the check valve adjusts the check direction of the fluid medium to the opposite direction. At the same time, the lock pin 605 in the limit assembly 6 is inserted into the lock groove 606 at the corresponding position to limit the angle of the rotating part 3, ensuring that the valve disc assembly 5 is located in the correct position. When the rotating part 3 rotates, the pulley 6051 arranged under the lock pin 605 reduces the friction and wear of the lock pin 605 during rotation, thereby increasing the service life. Similarly, if the worker installs the check valve in the opposite direction when installing the check valve, the worker can also correct and adjust the fluid check direction of the check valve according to the above principle. Through the cooperation between the above structures, the fluid check direction of the check valve can be changed accordingly according to production needs, without relying on the addition of external pipelines, thereby reducing material costs, reducing the occupied space of the equipment, and making the adjustment process convenient, thereby reducing maintenance costs, making the check valve more flexible and scalable, and also improving the production efficiency of the enterprise. ;

[0039] Further, the fixed plate 7 is composed of a first fixed ring 701 and a second fixed ring 702 assembled and fixed, and the damping mechanism 8 includes a first cavity 801 and a second cavity 802 respectively provided on opposite surfaces of the first fixed ring 701 and the second fixed ring 702, and a sealing baffle 803 for sealing the first cavity 801 and the second cavity 802 is fixedly assembled on the opposite surfaces of the first fixed ring 701 and the second fixed ring 702, and both sides of the sealing baffle 803 are provided with a sealing ring 8032 for improving the sealing performance, and a plurality of through holes 8031 ​​for connecting the first cavity 801 and the second cavity 802 are provided on the sealing baffle 803, and a piston group is slidably provided in the second cavity 802. The piston assembly 8021 comprises a piston seat 80211 and a sealing piston 80212. The piston seat 80211 is linked to the connecting rod 501 through the connecting rod 5011. When the valve flap 502 is opened, the piston assembly 8021 presses the air in the second cavity 802 into the first cavity 801 through the through hole 8031. When the valve flap 502 is closed, the piston assembly 8021 is located at the beginning of the stroke in the second cavity 802, and several through holes 8031 ​​are exposed. When the valve flap 502 is opened, the piston assembly 8021 moves to the end of the stroke in the second cavity 802, and several through holes 8031 ​​are gradually blocked by the piston assembly 8021. When the fluid passes through the check valve, the pressure of the fluid presses the valve flap. When valve 502 is opened, the pressure imbalance of the fluid in the pipeline often causes the valve flap 502 to swing up and down. The frequent swinging of the valve flap 502 will first loosen the fasteners of the valve flap 502 and damage the connection of the valve flap 502. At the same time, the up and down swinging of the valve flap 502 may also cause impact on the pipeline system, increase the vibration and noise of the pipeline system, and may cause loosening or leakage of the pipeline connection in the long run. In addition, the up and down swinging of the valve flap 502 will interfere with the normal flow of the fluid, resulting in instability of the fluid flow rate and pressure. This unstable state may cause turbulence and eddy currents of the fluid, increase the loss of pipeline transportation energy, reduce fluid transportation efficiency, and cause safety problems such as water hammer, which will cause a huge impact on the pipeline system and may even cause pipeline rupture or leakage. Serious accidents, in order to solve this problem, when the fluid passes through the valve body 1, the valve disc 502 opens, and the connecting rod 501 swings at the same time, and the connecting rod 501 drives the piston assembly 8021 to move in the second cavity 802, and the piston assembly 8021 squeezes the air in the second cavity 802 into the first cavity 801 through a plurality of through holes 8031, and when the water flow pressure gradually opens the valve disc 502, the connecting rod 501 drives the piston seat 80211 and the sealing piston 80212 to move, and the piston seat 80211 gradually moves from the beginning of the stroke to the end of the stroke, and the sealing piston 80212 also gradually blocks the plurality of through holes 8031 ​​(the size of the sealing piston 80212 can seal and block all the through holes 8031 ​​when it moves to the end of the stroke).That is, when the piston assembly 8021 gradually moves from the stroke beginning end to the stroke end end of the second cavity 802, the number of through holes 8031 ​​in the second cavity 802 that squeeze the air into the first cavity 801 gradually decreases, that is, when the valve flap 502 is opened, the passage for air to enter the first cavity 801 gradually decreases, and the valve flap 502 is provided with a buffer under the action of air pressure, so that the valve flap 502 has damping when it is opened, preventing the valve flap 502 from swinging greatly when the fluid pressure is unbalanced. The damping effect of the above structure changes with the opening degree of the valve flap 502, because the through hole 8031 ​​is gradually blocked, and the valve flap 502 is prevented from swinging greatly when the fluid pressure is unbalanced. This reduces the gas flow channel, thereby increasing the damping force. This design allows the damping force to be naturally adjusted at different stages of the piston assembly 8021 stroke without the need for an external control mechanism, providing a more flexible and dynamic damping response. In the early stage of the rapid swing of the valve flap 502, a large amount of gas flows from the first cavity 801 to the second cavity 802 through the through hole 8031. The damping is small and does not affect the normal opening of the valve flap 502. As the piston assembly 8021 moves, the gas flow is restricted, which helps to absorb and disperse the impact energy, reduce vibration and noise in the mechanical system, and effectively solve the above-mentioned problems.

[0040] Furthermore, a sealing plug 5021 corresponding to the valve seat 102 at the flow channel of the valve body 1 is fixedly provided on one side of the valve flap 502, and a soft cushion 5022 for preventing the valve flap 502 from colliding with the valve body 1 is fixedly provided on one side of the valve flap 502. When the valve flap 502 is fully opened, in order to prevent the connecting rod 501 from being damaged by hard contact with the valve body 1 when it swings to the end of the stroke, the soft cushion 5022 arranged behind the valve flap 502 can provide good buffering for it, thereby greatly improving the service life of the equipment. When the valve flap 502 is closed, the sealing plug 5021 will be inserted into the valve seat 102 to provide sealing for it, and can also provide buffering for it when the valve flap 502 is closed.

[0041] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0042] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. A swing check valve, comprising a valve body (1), wherein two ends of the valve body (1) are respectively a first liquid port (01) and a second liquid port (02), wherein: The valve body (1) is rotatably mounted with a rotating part (3) whose angle can be adjusted relative to the valve body (1) via a rotating assembly (2); the rotating part (3) is fixedly mounted with an upper cover (4); a fixing plate (7) is fixedly mounted at a mounting hole on the rotating part (3); a rotating column (700) is rotatably mounted on the fixing plate (7) via a bearing; one end of the rotating column (700) extends into the interior of the rotating part (3), and a valve flap assembly (5) is fixedly mounted on the end; an adjusting mechanism (9) for adjusting the angle of the rotating column (700) is arranged on the fixing plate (7); an adjustment area (101) for rotating the valve flap assembly (5) is arranged inside the valve body (1), and a limit assembly (6) for limiting the position of the rotating part (3) is also included.

2. A swing check valve according to claim 1, characterized in that: The rotating assembly (2) comprises a rotating sleeve (201), and an upper flange (202) rotatably arranged thereon and a lower flange (203) below, wherein the upper flange (202) and the lower flange (203) are respectively fixedly connected to the rotating part (3) and the valve body (1) via fixing bolts.

3. A swing check valve according to claim 2, characterized in that: The limit assembly (6) comprises a shell (601), a moving block (603) is slidably arranged in the shell (601) via a tension spring (602), a button (604) is arranged at one end of the moving block (603), a locking pin (605) is movably arranged in the shell (601), one end of the locking pin (605) extends to the outside of the shell (601), a locking groove (606) cooperating with the locking pin (605) is provided on the upper flange (202), a driving surface (6031) for the locking pin (605) to move and open and close is provided on the moving block (603), and the tension spring (602) is used to drive the moving block (603) so that the driving surface (6031) inserts the locking pin (605) into the locking groove (606).

4. A swing check valve according to claim 3, characterized in that: A pulley (6051) is rotatably provided at one end of the locking pin (605) opposite to the driving surface (6031).

5. A swing check valve according to claim 3, characterized in that: The adjusting mechanism (9) comprises an adjusting nut (900) fixedly arranged at one end of a rotating column (700), a locking column (901) slidingly passing through the adjusting nut (900), and a positioning groove (902) provided on one side of the fixed disk (7) and correspondingly cooperating with the locking column (901), an adjusting block (903) for opening and closing the locking column (901) being arranged at one end of the locking column (901) by rotating through a rotating shaft, and a reset spring (904) for resetting the locking column (901) being terminated between the other end of the locking column (901) and the adjusting nut (900).

6. A swing check valve according to claim 1, characterized in that: The valve flap assembly (5) comprises a connecting rod (501), wherein the connecting rod (501) is rotatably mounted on one side of a fixed disk (7) via a rotating column (700), a valve flap (502) is fixedly mounted on the connecting rod (501) via fixing bolts, and a damping mechanism (8) is provided on the fixed disk (7) for providing damping to the valve flap assembly (5).

7. A swing check valve according to claim 6, characterized in that: The fixed plate (7) is composed of a first fixed ring (701) and a second fixed ring (702) assembled and fixed, and the damping mechanism (8) comprises a first cavity (801) and a second cavity (802) respectively provided on opposite surfaces of the first fixed ring (701) and the second fixed ring (702), and a sealing baffle (803) for sealing the first cavity (801) and the second cavity (802) is fixedly mounted on opposite surfaces of the first fixed ring (701) and the second fixed ring (702), and both sides of the sealing baffle (803) are A sealing ring (8032) is provided for improving the sealing performance. The sealing baffle (803) is provided with a plurality of through holes (8031) for connecting the first cavity (801) and the second cavity (802). A piston assembly (8021) is slidably provided in the second cavity (802). The piston assembly (8021) is linked to the connecting rod (501). When the valve flap (502) is opened, the piston assembly (8021) presses the air in the second cavity (802) into the first cavity (801) through the through hole (8031).

8. A swing check valve according to claim 7, characterized in that: When the valve flap (502) is closed, the piston assembly (8021) is located at the beginning of the stroke in the second cavity (802), and the plurality of through holes (8031) are exposed; when the valve flap (502) is opened, the piston assembly (8021) moves toward the end of the stroke in the second cavity (802), and the plurality of through holes (8031) are gradually blocked by the piston assembly (8021).

9. A swing check valve according to claim 6, characterized in that: A sealing plug (5021) corresponding to the valve seat (102) at the flow channel of the valve body (1) is fixedly provided on one side of the valve flap (502).

10. The swing check valve according to claim 6, characterized in that: A soft cushion (5022) is fixedly provided on one side of the valve flap (502) for preventing the valve flap (502) from colliding with the valve body (1).

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