A gate valve with dual valve core and valve seat and its sealing method

Abstract

This invention discloses a gate valve with dual valve core and seat, and a sealing method thereof, belonging to the field of high, medium, and low pressure pipeline transportation technology. The gate valve includes a valve body, a handwheel, a transmission mechanism, a valve stem, and a sealing mechanism. The valve body has an installation hole and two inlet / outlet holes respectively connected to the installation hole. The sealing mechanism includes a first valve seat, a first valve core, a valve core transmission assembly, a second valve core, and a second valve seat connected in sequence. The handwheel is connected to the first end of the valve stem, and the end of the valve stem is connected to the first valve core. When the valve stem pushes the first valve core to the end, the second valve core moves to the first end, and the two valve cores separate from the valve seats to open the two inlet / outlet holes. When the valve stem drives the first valve core to the first end, the second valve core moves to the end, and the two valve cores respectively seal the sealing surfaces of the valve seats to isolate the two inlet / outlet holes. The sealing mechanism forms two sets of sealing surfaces, achieving dual sealing, improving the sealing effect, and ensuring the normal operation of the overall system.

Description

Technical Field

[0001] This invention belongs to the field of high, medium and low pressure pipeline transportation technology, specifically relating to a shut-off valve with a dual valve core and valve seat and a sealing method. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] In industrial production and fluid transport systems, gate valves are a key control element, widely used in many fields such as petroleum, chemical, power, and water supply and drainage.

[0004] With industrial development, the requirements for automation and continuous production processes are increasing, leading to a corresponding increase in the frequency and duration of use of gate valves. Frequent switching operations and prolonged operating conditions place greater challenges on valve core seals, such as accelerated wear between the valve core and seat, and aging of sealing materials. These issues can cause a decline in sealing performance, thereby affecting the normal use of the gate valve and the stable operation of the entire system.

[0005] Existing gate valves, often described as having a single valve core and seat seal, rely on a single compression seal. If hard particles in the medium are present and become trapped on the valve core and seat sealing surfaces, they can cause scratches and lead to leakage. Frequent opening and closing can also cause wear and tear on the valve core and seat, resulting in further leakage. Once leakage occurs due to valve core wear or other reasons during use, the gate valve will malfunction, affecting the overall system's operation, resulting in low stability, reliability, and a short service life.

[0006] Therefore, how to provide a gate valve with excellent sealing performance, stable and reliable operation and long service life is a technical problem that needs to be solved by those skilled in the art. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a gate valve with dual valve cores and valve seats and a sealing method. In the opening and closing process, the gate valve provided by the present invention features synchronous movement of the dual valve cores and a dual valve core and valve seat for sealing, resulting in a good sealing effect.

[0008] To achieve the above objectives, the technical solution of the present invention is as follows:

[0009] In a first aspect, the present invention provides a gate valve with a dual valve core and seat, comprising a valve body, a handwheel, a transmission mechanism, a valve stem, and a sealing mechanism. The valve body has an installation hole and two inlet / outlet holes respectively connected to the installation hole. The sealing mechanism is disposed within the installation hole and includes a first valve seat, a first valve core, a valve core transmission assembly, a second valve core, and a second valve seat connected in sequence. The handwheel is connected to the head end of the valve stem via the transmission mechanism. The tail end of the valve stem is connected to the first valve core. When the valve stem pushes the first valve core towards the second valve core, the second valve core moves towards the first valve core under the drive of the valve core transmission assembly. The two valve cores respectively leave the valve seat to open the two inlet / outlet holes. The valve stem drives the first valve core to move away from the second valve core, and the second valve core moves away from the first valve core under the drive of the valve core transmission assembly. The two valve cores respectively seal the sealing surfaces of the valve seats to isolate the two inlet / outlet holes.

[0010] In some embodiments of the present invention, the mounting hole extends along the axis of the shut-off valve, and the two inlet and outlet holes are axially offset from the openings of the sidewall of the mounting hole.

[0011] In some embodiments of the present invention, the valve core transmission assembly includes a first connecting rod, a second connecting rod, a transmission wheel, and a transmission shaft. The transmission wheel is sleeved on the transmission shaft and rotates around the transmission shaft. The first connecting rod and the second connecting rod are disposed on both sides of the transmission wheel. The rotation of the transmission wheel drives the first connecting rod and the second connecting rod to move in opposite directions. The transmission shaft is connected to the valve body.

[0012] In some embodiments of the present invention, the first connecting rod and the transmission wheel, and the second connecting rod and the transmission wheel are all connected by a gear and rack transmission.

[0013] In some embodiments of the present invention, the valve body is further provided with a sealing device, which is sleeved on the outside of the valve stem and disposed in the mounting hole above the sealing mechanism.

[0014] In some embodiments of the present invention, the sealing device is a valve stem sealing ring.

[0015] In some embodiments of the present invention, the valve stem end is provided with a valve stem thrust mechanism, the end of which is fixedly connected to the first valve core. The valve stem thrust mechanism is composed of three cylinders of different diameters fixedly arranged in descending order of diameter. The centers of the bottom circles of the three cylinders are on the same straight line. The cylinder with the largest diameter is connected to the end of the valve stem, and its diameter is the diameter of the mounting hole. The diameters of the remaining two cylinders are smaller than the diameter of the through hole in the first valve seat, and the cylinder with the smallest diameter is connected to the first valve core.

[0016] Preferably, the cylinder with the smallest diameter is embedded in the first valve core.

[0017] In some embodiments of the present invention, the shut-off valve further includes a valve cover, which is disposed above the valve body and fixedly connected to the valve body. The valve stem passes through the valve cover and is connected to the transmission mechanism. The top of the valve cover is provided with a groove for installing the transmission mechanism.

[0018] The transmission mechanism includes a drive nut, a drive bearing, and a bearing cap. Part of the drive nut is disposed in a groove on the top of the valve cover and sleeved on the first end of the valve stem, and part is fixedly connected to the handwheel. The drive bearing is disposed in the groove and sleeved on the drive nut. The bearing cap is disposed on the drive nut and disposed on the top of the valve cover to fix the drive bearing. The handwheel, drive nut, and drive bearing cooperate to allow the drive nut to move up and down in the groove by rotation.

[0019] In some embodiments of the present invention, the valve cover is fixed to the valve body by bolts.

[0020] In a second aspect, the present invention provides a sealing method, which employs the aforementioned shut-off valve, connects a pipe to an inlet / outlet port, and rotates a handwheel to move the valve stem upward, causing the first valve core to seal the first valve seat upward and the second valve core to seal the second valve seat downward, thus isolating the two inlet / outlet ports and achieving a seal; rotating the handwheel to move the valve stem downward causes the first valve core to move downward away from the first valve seat and the second valve core to move upward away from the valve seat, thus connecting the two inlet / outlet ports and achieving communication.

[0021] The beneficial effects of this invention are as follows:

[0022] This invention provides a sealing method for a gate valve with dual valve core and seat seals. The method employs a synchronously moving dual valve core and seat sealing structure to improve the reliability of the internal seal of the gate valve. During the opening and closing of the gate valve, the two valve cores move synchronously, resulting in a dual valve core and seat seal and excellent sealing performance. If one valve core or seat experiences wear and leakage, the other valve core and seat sealing mechanism can still maintain a sealing effect, demonstrating a high fault tolerance rate. This dual valve core and seat sealing method for gate valves improves the internal sealing effect and media delivery fault tolerance rate of the gate valve, solves the problem of leakage caused by valve core and seat wear during the use of existing gate valves, ensures valve safety and production safety, and improves production operation efficiency.

[0023] The dual valve core and seat sealing gate valve provided by this invention provides a self-sealing first valve core and seat when the valve is closed or when the second valve core and seat are damaged. The first valve core and seat become tighter under the pressure of the medium, resulting in a good sealing effect. Attached Figure Description

[0024] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0025] Figure 1 This is a schematic diagram of the structure of the gate valve with dual valve core and valve seat seal according to Embodiment 1 of the present invention;

[0026] Figure 2 for Figure 1 Enlarged view of part A in the middle.

[0027] In the diagram, 1-valve body; 2-second valve seat; 3-second valve core; 4-second connecting rod; 5-drive wheel; 6-drive shaft; 7-first connecting rod; 8-first valve core; 9-first valve seat; 10-valve stem thrust mechanism; 11-valve stem sealing ring; 12-valve cover; 13-valve stem; 14-drive nut; 15-drive bearing; 16-bearing cover; 17-handwheel; 18-mounting hole; 19-inlet / outlet hole. Detailed Implementation

[0028] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0029] Please see Figure 1 and Figure 2 ,in, Figure 1 This is a schematic diagram of the structure of the dual valve core and valve seat described in this embodiment. Figure 2 for Figure 1 An enlarged view of part A in the structural schematic diagram shown.

[0030] A typical embodiment of the present invention provides a shut-off valve with a dual valve core and valve seat, such as... Figure 1 As shown, this dual-core valve seat shut-off valve includes a valve body 1, a handwheel 17, a transmission mechanism, a valve stem 13, and a sealing mechanism. The end of each component closest to the handwheel 17 is defined as the beginning end, and the end closest to the valve body 1 as the end end. The beginning and end ends of the valve body 1 extend sequentially from the other components. In the accompanying drawings, the upper end is the beginning end, and the lower end is the end end. The valve body 1 has a mounting hole 18 that extends axially. The opening at the beginning end is located on the end face of the valve body 1, and the closed opening at the end is located at the lower part of the valve body 1. The valve body 1 also has two inlet / outlet holes 19 that connect to the mounting hole 18. The inner ports of the two inlet / outlet holes 19 connect to the mounting hole 18, and the outer ports of the two inlet / outlet holes 19 are located on opposite sides of the outer periphery of the valve body 1. The outer openings of the two inlet / outlet holes 19 are used to connect the inlet pipe and the outlet pipe. When liquid flows, it flows sequentially through the inlet pipe, one inlet / outlet hole 19, the mounting hole 18, the other inlet / outlet hole 19, and the outlet pipe.

[0031] The sealing mechanism is disposed within the mounting hole 18 and includes a first valve seat 9, a first valve core 8, a valve core drive assembly, a second valve core 3, and a second valve seat 2 connected in sequence. The sealing mechanism, located between the inner openings of the two inlet / outlet holes 19, is a crucial component for isolating the two inlet / outlet holes 19. The diameters of the first valve seat 9 and the second valve seat 2 are the same as the diameter of the mounting hole 18. The two valve seats are fixed within the mounting hole 18, and each valve seat has a through hole at its center to facilitate liquid flow. The diameters of the two valve cores are larger than the diameter of the through holes to seal the valve seats and ensure excellent sealing performance. The valve core drive assembly enables the two valve cores to move synchronously in opposite directions, further improving the sealing effect.

[0032] The handwheel 17 is connected to the head end of the valve stem 13 via the transmission mechanism, and the tail end of the valve stem 13 is connected to the first valve core 8. Rotating the handwheel 17 forward drives the valve stem 13 axially toward its tail end via the transmission mechanism. Further, when the valve stem 13 pushes the first valve core 8 toward the second valve core 3, the second valve core 3 moves toward the first valve core 8 under the drive of the valve core transmission assembly. The two valve cores separate from the valve seat, thus opening the two inlet / outlet holes 19. Rotating the handwheel 17 in the reverse direction drives the valve stem 13 axially toward its head end via the transmission mechanism. Further, the valve stem 13 drives the first valve core 8 away from the second valve core 3. Under the drive of the valve core transmission assembly, the second valve core 3 moves away from the first valve core 8. The two valve cores seal the sealing surfaces of the valve seat, forming two sets of sealing surfaces to isolate the two inlet / outlet holes 19.

[0033] The gate valve achieves double sealing by forming two sets of sealing surfaces: the first valve seat 9 and the first valve core 8, and the second valve seat 2 and the second valve core 3. Compared to the single sealing of traditional gate valves, if one valve core or seat experiences wear and leakage, the other valve core or seat can still maintain a sealing effect, resulting in a high fault tolerance rate. Furthermore, either valve core or seat in the double valve core and seat structure is self-sealing. If the second valve core 3 experiences wear and leakage, the liquid medium in the outlet pipe enters the mounting hole 18, providing a certain pressure to the first valve core 8 and improving the sealing effect. If the first valve core 8 experiences wear and leakage, the liquid medium in the inlet pipe enters the mounting hole 18 and is stored above the second valve core 3, providing a certain pressure to the second valve core 3 and improving the sealing effect. Therefore, the double valve core and seat sealing gate valve improves the sealing effect and liquid medium delivery fault tolerance rate, solves the problem of leakage caused by valve core and seat wear during the use of existing gate valves, ensures valve safety and production safety, and improves production operation efficiency.

[0034] In some embodiments of this implementation, the mounting hole 18 extends along the axis of the shut-off valve, and the inner end openings of the two inlet and outlet holes 19 connected to the sidewall of the mounting hole 18 are axially offset. The sealing mechanism is located between the two openings, ensuring that the liquid flowing through the shut-off valve necessarily flows through the sealing mechanism. Specifically, the two inlet and outlet holes 19 can extend radially completely perpendicular to the axial direction, in which case the outer end openings of the two inlet and outlet holes 19 are also offset and not on the same straight line. Alternatively, the two inlet and outlet holes 19 can extend radially but not completely perpendicular to the axial direction; the upper inlet and outlet hole 19 can be inclined downwards, and the lower inlet and outlet hole 19 can be inclined upwards, so that the outer end openings of the two inlet and outlet holes 19 are on the same straight line, making the shut-off valve installation more convenient and the layout more reasonable.

[0035] In some embodiments of this implementation, the valve core transmission assembly includes a first connecting rod 7, a second connecting rod 4, a transmission wheel 5, and a transmission shaft 6. The transmission wheel 5 is sleeved on the transmission shaft 6 and rotates around the transmission shaft 6. The first connecting rod 7 and the second connecting rod 4 are disposed on both sides of the transmission wheel 5. The rotation of the transmission wheel 5 drives the first connecting rod 7 and the second connecting rod 4 to move in opposite directions. The transmission shaft 6 is connected to the valve body 1.

[0036] It should be noted that the first connecting rod 7, the second connecting rod 4, the transmission wheel 5, and the transmission shaft 6 together constitute the valve core transmission assembly. The first connecting rod 7 and the second connecting rod 4 are driven by the transmission wheel 5 to achieve synchronous operation. The first connecting rod 7, the second connecting rod 4, and the transmission wheel 5 can be connected by various transmission methods, such as gear and rack transmission or crank-connecting rod transmission.

[0037] like Figure 2 As shown, the first connecting rod 7, the second connecting rod 4, and the transmission wheel 5 are connected by a gear and rack mechanism. The transmission wheel 5 is a gear, which is sleeved on the transmission shaft 6 and rotates around the transmission shaft 6. The contact surfaces of the first connecting rod 7 and the second connecting rod 4 with the transmission wheel 5 are equipped with racks. When the transmission wheel 5 rotates, the meshing of the gear and rack drives the first connecting rod 7 and the second connecting rod 4 to move in opposite directions. Specifically, when the first connecting rod 7 moves downward under the downward thrust of the valve stem 13, it drives the transmission wheel 5 to rotate around the transmission shaft 6, and the second connecting rod 4 moves upward through the meshing of the gear and rack, causing the two valve cores to leave the sealing surface of the valve seat, thus achieving conduction. When the first connecting rod 7 moves upward under the upward pull of the valve stem 13, it drives the transmission wheel 5 to rotate around the transmission shaft 6, and the second connecting rod 4 moves downward through the meshing of the gear and rack, causing the two valve cores to seal the sealing surface of the valve seat, thus achieving a seal and closing the valve.

[0038] It should be noted that the first connecting rod 7, the second connecting rod 4 and the transmission wheel 5 can also be transmitted through a crank-connecting rod mechanism. The first connecting rod 7, the second connecting rod 4 and the transmission wheel 5 drive the valve core to move downward or upward, thereby achieving double sealing.

[0039] In some embodiments of this implementation, a sealing device is also provided inside the valve body, which is sleeved on the outside of the valve stem 13 and disposed in the mounting hole 18 above the sealing mechanism. Specifically, the sealing device is a valve stem sealing ring 11. The valve stem sealing ring 11 is sleeved on the outside of the valve stem 13, and the valve stem sealing ring 11 is located between the inner end opening of the upper inlet / outlet hole 19 and the top of the valve body 1, and the top end of the valve stem sealing ring 11 is flush with the top end of the valve body 1, so as to prevent liquid medium from flowing out from the top of the valve body 1 through the gap between the valve stem 13 and the valve body 1. The valve stem sealing ring 11 can be made of rubber, polytetrafluoroethylene, graphite, etc. Different materials have different temperature resistance, wear resistance, and corrosion resistance properties, and appropriate materials need to be selected according to the working environment and usage requirements.

[0040] In some embodiments of this implementation, a valve stem thrust mechanism 10 is provided at the end of the valve stem 13, and the end of the valve stem thrust mechanism 10 is fixedly connected to the first valve core 8. It can be understood that the valve stem thrust mechanism 10 is used to withstand the thrust of the valve stem 13, driving the first valve core 8 to move up and down, and also to prevent liquid medium from entering the gap between the valve stem 13 and the valve body sealing ring 11, thereby preventing liquid medium from leaking from the top of the valve body 1 and improving the sealing effect.

[0041] The valve stem thrust mechanism 10 consists of two parts. One part is a cylinder with a diameter equal to the mounting hole 18, connected to the valve stem 13, used to prevent liquid medium from leaking from the top of the valve body 1. The other part is a thrust rod installed below the cylinder. The diameter of the thrust rod is smaller than the diameter of the mounting hole 18, and the diameter of the end connected to the first valve core 8 is smaller than the diameter of the through hole on the valve body. The shape of the thrust rod is not limited in this invention, as long as it can transmit the force of the valve stem 13. For example, the thrust rod can be cylindrical, with the center of its base aligned vertically with the center of the cylinder's base. To improve the strength of the thrust rod and prevent damage due to excessive force, the thrust rod can be cake-shaped, constructed by stacking multiple cylinders of different diameters from top to bottom in descending order of diameter.

[0042] like Figure 1As shown, the valve stem thrust mechanism 10 is composed of three cylinders of different diameters fixed from top to bottom in descending order of diameter. The centers of the bottom circles of the three cylinders are on the same vertical line, and the centers of the bottom circles of the three cylinders are also on the same straight line as the center of the bottom circle of the valve stem 13, that is, the valve stem thrust mechanism 10 and the valve stem 13 are coaxially arranged. The cylinder with the largest diameter is connected to the end of the valve stem 13, and its diameter is the diameter of the mounting hole 18. The diameters of the remaining two cylinders are smaller than the diameter of the through hole in the first valve seat 9, and the cylinder with the smallest diameter (i.e., the end of the valve stem thrust mechanism 10) is connected to the first valve core 8 to transmit the force of the valve stem 13 to the first valve core 8.

[0043] It is understandable that the valve stem thrust mechanism 10 and the valve stem 13 are integrally formed. The diameter of the connection part between the valve stem thrust mechanism 10 and the valve 13 is enlarged to the diameter of the mounting hole 18, so as to prevent liquid medium from entering the gap between the valve stem 13 and the valve body sealing ring 11, thereby leaking from the top of the valve body 1.

[0044] Understandably, to prevent deformation or displacement of the first valve core 8 when the thrust rod pushes it downwards, the cylinder with the smallest diameter (i.e., the end of the valve stem thrust mechanism 10) is located directly above the center of gravity of the first valve core 8. To improve the transmission effect and the connection strength between the valve stem thrust mechanism 10 and the first valve core 8, the cylinder with the smallest diameter (i.e., the end of the valve stem thrust mechanism 10) can be embedded inside the first valve core 8. By increasing the contact area between the valve stem thrust mechanism 10 and the first valve core 8, the connection strength and force transmission effect are improved.

[0045] In some embodiments of the present invention, the shut-off valve further includes a valve cover 12. The valve cover 12 serves to: seal the valve body 1, press the valve stem sealing ring 11 to prevent liquid medium from leaking from the top of the valve body 1; and position the valve stem 13 to ensure normal transmission of the valve stem 13. The valve cover 12 is disposed above the valve body 1 and is fixedly connected to the valve body 1. The valve stem 13 passes through the valve cover 12 and is connected to the transmission mechanism. The top of the valve cover 12 is provided with a groove for installing the transmission mechanism.

[0046] like Figure 1As shown, the transmission mechanism includes a drive nut 14, a drive bearing 15, and a bearing cap 16. The drive bearing 15 can be a ball bearing, which supports and restricts the rotation direction of the drive nut 14. The bearing cap 16 mainly functions as an axial positioning element, dustproofing, and sealing element. The lower half of the drive nut 14 is disposed in a groove on the top of the valve cover 12 and is sleeved on the first end of the valve stem 13 to drive the valve stem 13 to move upward or downward. The upper half of the drive nut 14 is fixedly connected to a handwheel 17 to control the opening and closing of the shut-off valve by rotating the handwheel 17. The drive bearing 15 is disposed in the groove and sleeved on the drive nut 14. The groove has an internal thread, and the contact part of the drive nut 14 with the groove has an external thread, which meshes with the internal thread on the groove. When the handle 17 is rotated, it drives the drive nut 14 to rotate. By rotating in different directions, the drive nut 14 moves up and down in the groove, thereby realizing the opening and closing of the shut-off valve. The bearing cap 16 is mounted on the drive bearing 15 and is located at the top of the valve cover 12 to fix the drive bearing 15. The handwheel 17, drive nut 14 and drive bearing 15 cooperate to allow the drive nut 14 to move up and down in the groove by rotation, thereby switching from rotary motion to linear motion.

[0047] It is understood that the valve cover 12 and the valve body 1 can be fixed by bolts, and the connection method of the two components can also be adjusted according to the situation, all of which are within the protection scope of the present invention.

[0048] Another typical embodiment of the present invention provides a sealing method, which uses the above-mentioned shut-off valve to connect the pipeline to the inlet / outlet port 19. Specifically, the upper inlet / outlet port 19 is connected to the liquid inlet pipe, and the lower inlet / outlet port 19 is connected to the liquid outlet pipe.

[0049] When the valve is closed, turning the handwheel 17 rotates the drive bearing 15 and the drive nut 14, causing the drive nut 14 to rise within the groove. This moves the valve stem 13 towards its head, causing the first valve core 8 to move upward and contact the sealing surface of the first valve seat 9, achieving a first seal. Simultaneously, the second valve core 3 moves downward and contacts the sealing surface of the second valve seat 2, achieving a second seal. The entire process achieves a double seal, significantly increasing the sealing effect.

[0050] When opening the valve, turn the handwheel 17 in the opposite direction, causing the drive bearing 15 and drive nut 14 to rotate. This causes the drive nut 14 to descend within the groove, moving the valve stem 13 to its end. Continuing to rotate the handwheel 17 causes the first valve core 8 to move downwards away from the first valve seat 9, separating the sealing surface of the first valve core 8 from the sealing surface of the first valve seat 9. Simultaneously, the second valve core 3 moves upwards away from the second valve seat 2, separating the sealing surface of the second valve core 3 from the sealing surface of the second valve seat 2, thus opening the two inlet / outlet holes 19. After continuously rotating the handwheel 17 to the desired position, the valve is fully open.

[0051] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A shut-off valve with a dual valve core and valve seat, characterized in that, The device includes a valve body, a handwheel, a transmission mechanism, a valve stem, and a sealing mechanism. The valve body has a mounting hole and two inlet / outlet holes respectively connected to the mounting hole. The sealing mechanism is located within the mounting hole and includes a first valve seat, a first valve core, a valve core transmission assembly, a second valve core, and a second valve seat connected in sequence. The handwheel is connected to the beginning of the valve stem via the transmission mechanism. The end of the valve stem is connected to the first valve core. When the valve stem pushes the first valve core towards the second valve core, the second valve core moves towards the first valve core under the drive of the valve core transmission assembly. The two valve cores separate from the valve seats to open the two inlet / outlet holes. The valve stem also drives the first valve core to move away from the second valve core, and the second valve core moves away from the first valve core under the drive of the valve core transmission assembly. The two valve cores seal the sealing surfaces of the valve seats to isolate the two inlet / outlet holes. The valve core transmission assembly includes a first connecting rod, a second connecting rod, a transmission wheel, and a transmission shaft. The transmission wheel is sleeved on the transmission shaft and rotates around the transmission shaft. The first connecting rod and the second connecting rod are located on both sides of the transmission wheel. The rotation of the transmission wheel drives the first connecting rod and the second connecting rod to move in opposite directions. The transmission shaft is connected to the valve body. The valve stem end is provided with a valve stem thrust mechanism. The end of the valve stem thrust mechanism is fixedly connected to the first valve core. The valve stem thrust mechanism is composed of three cylinders of different diameters fixed in order of decreasing diameter. The centers of the bottom circles of the three cylinders are on the same straight line. The cylinder with the largest diameter is connected to the end of the valve stem, and its diameter is the diameter of the mounting hole. The diameters of the remaining two cylinders are smaller than the diameter of the through hole in the first valve seat, and the cylinder with the smallest diameter is connected to the first valve core. The cylinder with the smallest diameter is embedded in the first valve core; The valve body is also provided with a sealing device, which is sleeved on the outside of the valve stem and located in the mounting hole above the sealing mechanism; The sealing device is a valve stem sealing ring, which is sleeved on the outside of the valve stem. The valve stem sealing ring is located between the inner end opening of the upper inlet / outlet hole and the top of the valve body, and the top of the valve stem sealing ring is flush with the top of the valve body.

2. The shut-off valve with dual valve core and valve seat as described in claim 1, characterized in that, The mounting hole extends along the axis of the shut-off valve, and the two inlet and outlet holes are axially offset from the openings of the sidewall of the mounting hole.

3. The shut-off valve with dual valve core and valve seat as described in claim 1, characterized in that, The first connecting rod and the transmission wheel, as well as the second connecting rod and the transmission wheel, are connected by a gear and rack transmission.

4. The shut-off valve with dual valve core and valve seat as described in claim 1, characterized in that, The shut-off valve also includes a valve cover, which is disposed above the valve body and fixedly connected to the valve body. The valve stem passes through the valve cover and is connected to the transmission mechanism. The top of the valve cover is provided with a groove for installing the transmission mechanism. The transmission mechanism includes a drive nut, a drive bearing, and a bearing cap. Part of the drive nut is disposed in a groove on the top of the valve cover and sleeved on the first end of the valve stem, and part is fixedly connected to the handwheel. The drive bearing is disposed in the groove and sleeved on the drive nut. The bearing cap is disposed on the drive nut and disposed on the top of the valve cover to fix the drive bearing. The handwheel, drive nut, and drive bearing cooperate to allow the drive nut to move up and down in the groove by rotation.

5. The shut-off valve with a dual valve core and valve seat as described in claim 4, characterized in that, The valve cover is fixed to the valve body by bolts.

6. A sealing method, characterized in that, Using any one of the shut-off valves described in claims 1-5, the pipeline is connected to the inlet and outlet ports. Rotating the handwheel causes the valve stem to move upward, whereby the first valve core seals the first valve seat upward and the second valve core seals the second valve seat downward, thus isolating the two inlet and outlet ports and achieving a seal. Rotating the handwheel causes the valve stem to move downward, whereby the first valve core moves downward away from the first valve seat and the second valve core moves upward away from the valve seat, thus connecting the two inlet and outlet ports and achieving a connection.

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