Pneumatic stop valve

Abstract

The present invention relates to a pneumatic stop valve, which includes a valve seat portion, a valve core portion and a pneumatic actuator. According to the present invention, a first chamber is constructed in the fluid channel of the valve seat body, the first chamber is defined by the valve seat body and the valve stem and is equipped with a first sealing element that acts when the valve stem moves to close the fluid channel, so as to seal the fluid inlet and the fluid outlet; a second chamber is constructed in the valve tube of the valve core portion, the second chamber is defined by the valve tube and the valve stem and is equipped with a second sealing element that acts when the valve stem moves to open the fluid channel, so as to seal the valve seat portion and the valve tube of the valve core portion. The small air-driven high-pressure stop valve realized by the present invention has a simple structure, low cost, and is very suitable for scientific research institutions or laboratories.

Description

Technical Field

[0001] The present invention relates to the field of valve control technology. Specifically, the present invention relates to a pneumatic stop valve, in particular to a small high-pressure pneumatic stop valve suitable for use in high-pressure fluid control in scientific research institutions or laboratories. Background Art

[0002] Valves are the main control components in fluid delivery or air tightness detection systems, among which high-pressure stop valves are one of the most widely used valve types. At present, small high-pressure stop valves are mostly controlled manually, with low control accuracy and difficult to achieve automation. There are a small number of high-pressure pneumatic stop valve products on the market, but due to their complex structure, easy damage and large size, they are not suitable for use in scientific research institutions or laboratories. Summary of the invention

[0003] The purpose of the present invention is to develop a pneumatic stop valve, in particular a small high-pressure pneumatic stop valve suitable for use in scientific research institutions or laboratories in high-pressure fluid control, and to optimize the structural design of the valve to meet the market demand for such products.

[0004] To this end, the present invention provides a pneumatic stop valve, which includes:

[0005] A valve seat portion, wherein a valve seat body of the valve seat portion has a fluid inlet and a fluid outlet and a fluid channel connecting the fluid inlet and the fluid outlet;

[0006] a valve core portion connected to the valve seat portion and comprising a valve tube and a valve stem extending from the valve tube toward the valve seat body, the valve stem being capable of reciprocating in a guide hole of the valve tube; and

[0007] A pneumatic actuator, which is configured as a piston-type drive mechanism, has a piston rod connected to the valve stem, and can drive the valve stem to reciprocate through the piston rod to close or open the fluid channel;

[0008] It is characterized in that a first chamber is constructed in the fluid channel of the valve seat body, the first chamber is defined by the valve seat body and the valve stem, the first chamber is equipped with a first sealing element that acts between the valve seat body and the valve stem when the valve stem moves to close the fluid channel, so as to seal the fluid inlet and the fluid outlet; at the connecting portion between the valve seat portion and the valve core portion, a second chamber is constructed in the valve tube of the valve core portion, the second chamber is defined by the valve tube and the valve stem, the second chamber is equipped with a second sealing element that acts between the valve tube and the valve stem when the valve stem moves to open the fluid channel, so as to seal the valve tube of the valve seat portion and the valve core portion.

[0009] According to the present invention, by reasonably configuring the local structures of the valve core part (especially the valve stem) and the valve seat part (especially the valve seat body), the opening and closing control of the valve and the sealing action are coordinated and linked, thereby ensuring the reliable function of the valve while allowing its miniaturized design to be achieved.

[0010] It is preferably provided that: along the axial direction of the valve stem, the valve core part is coaxially arranged with the valve seat part and the pneumatic actuator, one end of the valve stem extends into the valve seat body, and the other end is connected to the piston rod of the piston drive mechanism, wherein the first sealing element and the second sealing element are subjected to axial pressure when the valve stem moves axially to close or open the fluid channel. In this way, the valve as a whole has a compact structural type, and at the same time, it is particularly advantageous that the axial force for operating the opening and closing movement of the valve stem can be fully used to implement the sealing function.

[0011] Advantageously, the first sealing element and the second sealing element are elastomeric seals, which produce corresponding sealing and isolating effects when subjected to axial pressure. The elastomeric seals are preferably O-rings. Therefore, in the technical solution proposed by the present invention, the sealing element is used as a sealing ring, and a universal standard part can be directly selected, thereby significantly reducing the manufacturing, use and maintenance costs of the product.

[0012] According to some embodiments of the present invention, the piston drive mechanism includes a piston sleeve and a piston that can reciprocate in the piston sleeve, the piston sleeve is provided with an air source interface at the top and is closed by a baffle at the bottom, the piston rod is connected to the lower part of the piston and is connected to the valve stem through the baffle, and a third sealing element is provided between the outer peripheral surface of the piston and the inner wall surface of the piston sleeve, so that an upper and a lower cavity that are sealed and isolated from each other are formed inside the piston sleeve, wherein the upper cavity is connected to the air source interface, and a spring is provided in the lower cavity that is sleeved on the piston rod. Here, the air source interface can be connected to an external compressed air source, and the pneumatic stop valve of the present invention can be used in various applications with a circulation pressure of up to 60MPa by adjusting the external air source. The spring can return the valve stem to a normal position when the air source is shut off, and at the same time, it is advantageously used to apply the pressure required for sealing.

[0013] Here, the spring may be a cylindrical helical compression spring, one end of which is supported by the piston and the other end is supported by the baffle. The cylindrical helical compression spring may be directly selected from universal standard parts. The spring may be installed in place with an appropriate preload force in consideration of the fluid working pressure and / or pneumatic control pressure of the valve.

[0014] Here, the third sealing element is preferably an O-ring installed on the outer circumference of the piston.

[0015] Here, the bottom of the piston sleeve abuts against the top of the valve tube, and the piston sleeve and the valve tube can be locked and connected to each other by screws.

[0016] Advantageously, the valve stem and the piston rod are constructed as one body. In this way, while ensuring reliable force transmission of the actuating component, a compact miniaturized design of the product can be achieved and the number of components can be reduced.

[0017] According to some embodiments of the present invention, a protrusion is formed at the bottom of the valve tube, and the valve seat body has a groove corresponding to the protrusion. The protrusion is matched with the groove to mount and fix the valve core part on the valve seat part.

[0018] Here, it is feasible that the protrusion of the valve tube is cylindrical and has an external thread on its outer circumference, and the groove of the valve seat body is circular and has an internal thread matching the external thread on its inner circumference. Thus, the valve tube (or the valve core) can be connected to the valve seat body (or the valve seat) through threaded engagement, achieving simple and reliable assembly and fixation of the two.

[0019] Regarding the first chamber and its sealing design, according to a specific embodiment of the present invention, the valve seat body has a first countersunk hole at the bottom of the groove, the end of the valve stem extends into the first countersunk hole, the end surface of the valve stem and the first countersunk hole jointly define the first chamber, and the first sealing element is arranged on the bottom surface of the first countersunk hole and is squeezed between the end surface of the valve stem and the bottom surface of the first countersunk hole when the valve stem moves axially to close the fluid passage. In this way, a simple and reliable end plane seal can be advantageously achieved to seal and isolate the fluid inlet from the fluid outlet.

[0020] Here, preferably, the side wall of the first counterbore has a hole connected to the fluid inlet, and the bottom surface of the first counterbore has a hole connected to the fluid outlet. Within the scope of the present invention, according to specific needs and installation conditions, the arrangement orientation of the fluid inlet and outlet and the arrangement and direction of the holes can take various different design forms, as long as their connection and functional relationship are maintained unchanged.

[0021] Regarding the second chamber and its sealing design, according to a specific embodiment of the present invention, the valve tube has a second countersunk hole on the end face of the protrusion, the second countersunk hole is axially adjacent to the guide hole of the valve tube, the valve stem is configured with a radially protruding shoulder at a position adjacent to the end portion thereof extending into the valve seat body, the valve stem defines the second chamber together with the second countersunk hole through the shoulder, and the second sealing element is arranged on the side of the shoulder facing the bottom surface of the second countersunk hole and is squeezed between the shoulder and the bottom surface of the second countersunk hole when the valve stem moves axially to open the fluid passage. In this way, a simple and reliable end plane seal can be advantageously achieved to seal and isolate the valve seat portion (i.e., the fluid medium side) from the valve tube of the valve core portion (i.e., the control mechanism side).

[0022] In this case, it is advantageous if the shaft shoulder has a groove for accommodating the second sealing element on its side facing the second countersunk hole bottom.

[0023] The pneumatic stop valve of the present invention can be constructed as a small high-pressure pneumatic stop valve, which is particularly suitable for the circulation and closing control of high-pressure gas or liquid in small-diameter process pipelines in laboratories of scientific research institutions. In particular, the technical solution proposed in this application can achieve at least one of the following beneficial technical effects:

[0024] (1) The overall structure is simple, compact and small in size;

[0025] (2) Few moving parts, not easy to damage;

[0026] (3) Simple manufacturing and assembly, low cost;

[0027] (4) Fewer design and control parameters, easy to modify, refit and transform, and achieve product line expansion;

[0028] (5) The sealing mechanism (especially the end plane sealing method) has a simple structure, reliable function and low cost;

[0029] (6) The maximum flow pressure can reach 60MPa, which can be widely adapted to various applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Some exemplary embodiments of the present invention are shown in the accompanying drawings. The embodiments and drawings disclosed herein should be regarded as illustrative rather than restrictive. It is also worth noting that for the sake of clarity of the drawings, some structural details in the drawings are not drawn according to the actual scale.

[0031] Figure 1 It is a structural schematic diagram of a preferred embodiment of the pneumatic stop valve of the present invention;

[0032] Figure 2 yes Figure 1 The schematic diagram of the working principle of the preferred embodiment of the pneumatic stop valve shown, wherein the valve is in a closed state;

[0033] Figure 3 yes Figure 1 The schematic diagram of the working principle of the preferred embodiment of the pneumatic stop valve is shown, wherein the valve is in the open state.

[0034] In the figure: 100. valve seat, 200. valve core, 300. pneumatic actuator, 1. valve seat body, 2. valve pipe, 3. piston sleeve, 4. screw, 5. air source interface, 6. piston, 7. third sealing element, 8. spring, 9. baffle, 10. valve stem, 11. second sealing element, 12. first sealing element, S1. first chamber, S2. second chamber DETAILED DESCRIPTION

[0035] The technical scheme of the embodiment of the present invention will be described below in conjunction with the accompanying drawings. Obviously, the described embodiment only relates to a part of the implementation forms of the present invention, rather than all of the implementation forms. Based on the embodiments disclosed in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0036] The terms "first", "second", "third", etc. in the specification and claims of the present application are used to distinguish different objects, rather than to describe a specific order. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions. For example, a process, method, product or device that includes a series of steps or units is not limited to the steps or units listed, but optionally includes steps or units that are not specifically listed, or optionally includes other steps or units inherent to these processes, methods, products or devices. It should be understood by those skilled in the art that in the description of the specification and claims of the present application, the orientation or position relationship indicated by certain terms such as "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "axial", "radial", "circumferential", etc. is based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device, mechanism, structure or element referred to must have a specific orientation, be constructed and operated in a specific orientation, so the above terms cannot be understood as limiting the present invention.

[0037] Reference to an "embodiment" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiment may be included in at least one implementation of the invention. The appearance of the term in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0038] Figure 1It is a structural schematic diagram of a preferred embodiment of the pneumatic stop valve of the present invention. The present invention provides a pneumatic stop valve, which includes: a valve seat portion 100, wherein the valve seat body 1 of the valve seat portion has a fluid inlet and a fluid outlet and a fluid channel connecting the fluid inlet and the fluid outlet; a valve core portion 200, wherein the valve core portion is connected to the valve seat portion and includes a valve tube 2 and a valve stem 10 extending from the valve tube to the valve seat body, and the valve stem can reciprocate in the guide hole of the valve tube; and a pneumatic actuator 300, wherein the pneumatic actuator is constructed as a piston-type drive mechanism, which has a piston rod connected to the valve stem 10, and can drive the valve stem to reciprocate through the piston rod to close or open the fluid channel. According to the present invention, a first chamber S1 is constructed in the fluid channel of the valve seat body 1, and the first chamber is defined by the valve seat body 1 and the valve stem 10. The first chamber is equipped with a first sealing element 12 that acts between the valve seat body 1 and the valve stem 10 when the valve stem moves to close the fluid channel, so as to seal the fluid inlet and the fluid outlet; at the connection portion between the valve seat portion and the valve core portion, a second chamber S2 is constructed in the valve tube 2 of the valve core portion 200, and the second chamber is defined by the valve tube 2 and the valve stem 10. The second chamber is equipped with a second sealing element 11 that acts between the valve tube 2 and the valve stem 10 when the valve stem moves to open the fluid channel, so as to seal the valve tube 2 of the valve seat portion 100 and the valve core portion 200.

[0039] According to the present invention, by reasonably configuring the local structures of the valve core part (especially the valve stem) and the valve seat part (especially the valve seat body), the opening and closing control of the valve and the sealing action are coordinated and linked, thereby ensuring the reliable function of the valve while allowing its miniaturized design to be achieved.

[0040] like Figure 1 As shown, along the axial direction of the valve stem 10, the valve core part 200 is coaxially arranged with the valve seat part 100 and the pneumatic actuator 300, one end of the valve stem 10 extends into the valve seat body 1, and the other end is connected to the piston rod of the piston drive mechanism, wherein the first sealing element 12 and the second sealing element 11 are respectively subjected to axial pressure when the valve stem moves axially to close or open the fluid channel. In this way, the valve as a whole has a compact structure, and at the same time, it is particularly advantageous that the axial force for operating the opening and closing movement of the valve stem can be fully applied to implement the sealing function. In this way, the valve as a whole has a compact structure, and at the same time, it is particularly advantageous that the axial force for operating the opening and closing movement of the valve stem can be fully applied to implement the sealing function.

[0041] According to the present invention, it is advantageous that the first sealing element 12 and the second sealing element 11 are elastomeric seals which produce corresponding sealing and isolating effects when subjected to axial pressure. The elastomeric seals are preferably O-rings.

[0042] According to the present invention, Figure 1 As shown, the piston drive mechanism includes a piston sleeve 3 and a piston 6 that can reciprocate in the piston sleeve. The piston sleeve 3 is provided with an air source interface 5 at the top and is closed by a baffle 9 at the bottom. The piston rod is connected to the lower part of the piston 6 and is connected to the valve stem 10 through the baffle 9. A third sealing element 7 is provided between the outer peripheral surface of the piston and the inner wall surface of the piston sleeve, so that an upper and a lower cavity that are sealed and isolated from each other are formed inside the piston sleeve, wherein the upper cavity is connected to the air source interface, and a spring 8 is provided in the lower cavity that is sleeved on the piston rod. Here, the air source interface can be connected to an external compressed air source. Through the external air source adjustment, the pneumatic stop valve of the present invention can be used in various applications with a circulation pressure of up to 60MPa. The spring can return the valve stem to a normal position when the air source is turned off, and at the same time, it is advantageously used to apply the pressure required for sealing. The spring is preferably a cylindrical helical compression spring, one end of which is supported by the piston 6 and the other end is supported by the baffle 9. The spring can be installed in place with an appropriate preload considering the fluid working pressure and / or pneumatic control pressure of the valve. The third sealing element 7 is preferably an O-ring installed on the outer periphery of the piston 6 .

[0043] like Figure 1 As shown, the bottom of the piston sleeve 3 is against the top of the valve tube 2 and the piston sleeve and the valve tube are locked and connected to each other by screws 4.

[0044] According to the present invention, it is particularly advantageous that the valve stem 10 and the piston rod are constructed as one piece. In this way, while ensuring reliable force transmission of the actuating component, a compact miniaturized design of the product can be achieved and the number of components can be reduced.

[0045] like Figure 1 As shown, a protrusion is formed at the bottom of the valve tube 2, and the valve seat body 1 has a groove corresponding to the protrusion. The protrusion is matched with the groove to make the valve core part 200 installed and fixed on the valve seat part 100. Preferably, the protrusion of the valve tube 2 is cylindrical and has an external thread on its outer circumference, and the groove of the valve seat body 1 is circular hole-shaped and has an internal thread matching the external thread on its inner circumference. Thus, the valve tube (or the valve core part) can be connected with the valve seat body (or the valve seat part) by screwing, so that the two can be simply and reliably assembled and fixed.

[0046] Regarding the first chamber S1 and its sealing design in the present invention, Figure 1As shown, the valve seat body 1 has a first countersunk hole at the bottom of the groove, the end of the valve stem 10 extends into the first countersunk hole, the end surface of the valve stem 10 and the first countersunk hole jointly define the first chamber S1, and the first sealing element 12 is arranged on the bottom surface of the first countersunk hole and is squeezed between the end surface of the valve stem and the bottom surface of the first countersunk hole when the valve stem moves axially to close the fluid passage. In this way, a simple and reliable end plane seal can be advantageously achieved to seal and isolate the fluid inlet from the fluid outlet. Preferably, the side wall of the first countersunk hole has a channel connected to the fluid inlet, and the bottom surface of the first countersunk hole has a channel connected to the fluid outlet.

[0047] Of course, the design of the fluid inlet and outlet and the communicating channels in the valve seat body is not limited to the specific manner described or illustrated. Within the scope of the present invention, the arrangement orientation of the fluid inlet and outlet and the arrangement and direction of the channels can adopt various different design forms according to specific needs and installation conditions, as long as their connection and functional relationship remain unchanged.

[0048] Regarding the second chamber S2 and its sealing design in the present invention, Figure 1 As shown, the valve tube 2 has a second countersunk hole on the end face of the protrusion, and the second countersunk hole is axially adjacent to the guide hole of the valve tube. The valve stem 10 is constructed with a radially protruding shoulder at a position adjacent to the end thereof extending into the valve seat body. The valve stem defines the second chamber S2 together with the second countersunk hole through the shoulder. The second sealing element 11 is arranged on the side of the shoulder facing the bottom surface of the second countersunk hole and is squeezed between the shoulder and the bottom surface of the second countersunk hole when the valve stem moves axially to open the fluid channel. In this way, a simple and reliable end plane seal can be advantageously achieved to seal and isolate the valve seat portion (i.e., the fluid medium side) from the valve tube of the valve core portion (i.e., the control mechanism side). Preferably, the shoulder has a groove for accommodating the second sealing element 11 on its side facing the bottom surface of the second countersunk hole.

[0049] Figure 2 yes Figure 1 The schematic diagram of the working principle of the preferred embodiment of the pneumatic stop valve shown, wherein the valve is in a closed state; Figure 3 yes Figure 1 The schematic diagram of the working principle of the preferred embodiment of the pneumatic stop valve is shown, wherein the valve is in the open state. Figure 2 and Figure 3 The hollow arrows in the figure indicate the access of high pressure fluid (gas or liquid). The pneumatic stop valve of the present invention can realize the opening and closing control of the valve in the following ways:

[0050] When the external air source is connected, the piston 6 is driven to compress the spring 8, driving the piston rod / valve stem 10 to move downward, and the bottom end surface of the valve stem squeezes the sealing ring on the bottom surface of the valve seat countersunk hole, the fluid channel in the valve seat body 1 is cut off, and the valve is in a closed state;

[0051] When the external gas source is cut off, the piston 6 is reset by the rebound force of the spring 8, driving the piston rod / valve stem 10 to move upward. The sealing ring between the valve stem 10 and the valve tube 2 produces a sealing effect. At this time, the fluid channel is opened and the valve is in an open state.

[0052] Thus, a new type of small pneumatic high-pressure stop valve can be realized, see Figure 1 , which includes a valve seat body 1, a valve stem 10, a valve tube 2, a piston 6, a piston sleeve 3, a spring 8, a sealing ring A (i.e., a third sealing element 7), a sealing ring B (i.e., a second sealing element 11), a sealing ring C (i.e., a first sealing element 12), an air source interface 5, and a screw 4. The valve seat body 1 is connected to the valve tube 2 by threads, and both ends of the valve seat body 1 are fluid inlet and outlet interfaces. A sealing countersunk hole is provided in the middle of the valve seat body 1 and the connecting part of the valve tube 2. The bottom of the sealing countersunk hole is connected to the fluid inlet and outlet, and a sealing ring C (i.e., a first sealing element 12) is arranged at the bottom of the countersunk hole of the valve seat body 1; the valve stem 10 is connected to the upper piston 6 through the central hole of the valve tube 2, the baffle 9 and the spring 8, and a sealing ring B (i.e., a second sealing element 11) is arranged at the T-shaped back of the bottom end area of ​​the valve stem 10; the piston 6 connected to the valve stem 10 is arranged in the piston sleeve 3, and a sealing ring A (i.e., a third sealing element 7) is arranged between the two, and a driving air source interface 5 is arranged at the top of the piston sleeve 3 to form an air-driven piston mechanism. The piston sleeve 3 and the valve tube 2 are fastened together by (multiple) screws 4 .

[0053] The sealing ring B (i.e., the second sealing element 11) disposed between the valve stem 10 and the valve tube 2 acts when the valve stem moves to open the fluid passage, thereby sealingly isolating the valve seat portion from the valve tube of the valve core portion.

[0054] The sealing ring C (ie, the first sealing element 12) disposed between the valve stem 10 and the valve seat body 1 works when the valve stem moves to close the fluid passage, thereby sealingly isolating the fluid inlet from the fluid outlet.

[0055] The working principle of this small pneumatic high pressure stop valve is as follows:

[0056] See also Figure 2 When the external air source is connected, the external air source pressure P1 on the piston 6 is greater than the spring pressure P2, so the air source drives the piston 6 to compress the spring 8, driving the valve stem 10 to move downward, and the bottom end surface of the valve stem 10 squeezes the sealing ring C on the bottom surface of the valve seat countersunk hole, the fluid channel in the valve seat body 1 is cut off, and the valve is placed in a closed state;

[0057] See also Figure 3 When the external air source is cut off, the spring pressure P2 on the piston 6 is greater than the external air source pressure P1 (P1=0), so the spring 8 rebounds and resets, pushing the piston 6 and driving the valve stem 10 to move upward, so that the sealing ring B arranged on the T-shaped back of the bottom end area of ​​the valve stem fits with the bottom surface of the valve tube countersunk hole, and the sealing ring B is further pressed against the bottom surface of the valve tube countersunk hole due to the force applied to the bottom of the valve stem by the high-pressure fluid, thereby enhancing the sealing effect. At this time, the fluid channel in the valve seat body 1 is opened, and the valve is placed in an open state.

[0058] It should be noted that within the framework of the present invention, the structure of the pneumatic stop valve can be straight-through, direct-flow and right-angle, and is not limited to the specific situation described / illustrated. For this purpose, it is only necessary to design the orientation of the fluid inlet and outlet and the arrangement and direction of the channel accordingly. Furthermore, the pneumatic stop valve of the present invention can be designed not only as a normally open type, but also as a normally closed type. For this purpose, the pneumatic actuator needs to be adapted accordingly, for example, the power gas chamber of the piston drive mechanism and the spring action chamber can be interchanged.

[0059] The above description of the embodiments is only used to help understand the core idea of ​​the present invention. Of course, for those skilled in the art, various modifications or supplements can be made to the specific embodiments described, or similar methods can be used to replace them according to the idea of ​​the present invention, without departing from the spirit of the present invention or exceeding the scope defined by the attached claims.

Claims

1. A pneumatic stop valve, comprising: A valve seat portion (100), wherein a valve seat body (1) of the valve seat portion has a fluid inlet and a fluid outlet, and a fluid channel connecting the fluid inlet and the fluid outlet; A valve core part (200), the valve core part being connected to the valve seat part and comprising a valve tube (2) and a valve stem (10) extending from the valve tube toward the valve seat body, the valve stem being capable of reciprocating in a guide hole of the valve tube; and A pneumatic actuator (300), the pneumatic actuator being constructed as a piston-type drive mechanism, having a piston rod connected to the valve stem (10), and capable of driving the valve stem to reciprocate through the piston rod to close or open the fluid channel; The invention is characterized in that a first chamber (S1) is constructed in the fluid passage of the valve seat body (1), the first chamber is defined by the valve seat body (1) and the valve stem (10), and the first chamber is provided with a first sealing element (12) which acts between the valve seat body (1) and the valve stem (10) when the valve stem moves to close the fluid passage, so as to seal the fluid inlet and the fluid outlet; a second chamber (S2) is constructed in the valve tube (2) of the valve core part (200) at the connection part between the valve seat part and the valve core part, the second chamber is defined by the valve tube (2) and the valve stem (10), and the second chamber is provided with a second sealing element (11) which acts between the valve tube (2) and the valve stem (10) when the valve stem moves to open the fluid passage, so as to seal the valve tube (2) of the valve seat part (100) and the valve core part (200); A protrusion is formed at the bottom of the valve tube (2), and the valve seat body (1) has a groove corresponding to the protrusion, and the protrusion is matched and connected with the groove so that the valve core part (200) is installed and fixed on the valve seat part (100); The valve seat body (1) has a first countersunk hole at the bottom of the groove, the end of the valve stem (10) extends into the first countersunk hole, the end surface of the valve stem (10) and the first countersunk hole jointly define the first chamber (S1), and the first sealing element (12) is arranged on the bottom surface of the first countersunk hole and is squeezed between the end surface of the valve stem and the bottom surface of the first countersunk hole when the valve stem moves axially to close the fluid passage; The valve tube (2) has a second countersunk hole on the end face of the projection, the second countersunk hole is axially adjacent to the guide hole of the valve tube, the valve stem (10) is constructed with a radially protruding shoulder at a position adjacent to its end extending into the valve seat body, the valve stem defines the second chamber (S2) together with the second countersunk hole through the shoulder, and the second sealing element (11) is arranged on the side of the shoulder facing the bottom surface of the second countersunk hole and is squeezed between the shoulder and the bottom surface of the second countersunk hole when the valve stem moves axially to open the fluid channel.

2. The pneumatic stop valve according to claim 1, characterized in that: Along the axial direction of the valve stem (10), the valve core portion (200) is coaxially arranged with the valve seat portion (100) and the pneumatic actuator (300), one end of the valve stem (10) extends into the valve seat body (1), and the other end is connected to the piston rod of the piston drive mechanism, wherein the first sealing element (12) and the second sealing element (11) are respectively subjected to axial pressure when the valve stem moves axially to close or open the fluid channel.

3. The pneumatic stop valve according to claim 2, characterized in that: The first sealing element (12) and the second sealing element (11) are elastomeric seals, which produce corresponding sealing and isolation effects when subjected to axial pressure.

4. The pneumatic stop valve according to claim 3, characterized in that: The elastomeric sealing element is an O-ring.

5. The pneumatic stop valve according to claim 1, characterized in that: The piston drive mechanism comprises a piston sleeve (3) and a piston (6) capable of reciprocating in the piston sleeve, wherein the piston sleeve (3) is provided with an air source interface (5) at the top and is sealed at the bottom by a baffle (9), a piston rod is connected to the lower part of the piston (6) and passes through the baffle (9) to be connected to a valve stem (10), a third sealing element (7) is provided between the outer peripheral surface of the piston and the inner wall surface of the piston sleeve, thereby forming an upper and a lower cavity inside the piston sleeve that are sealed and isolated from each other, wherein the upper cavity is communicated with the air source interface, and the lower cavity is provided with a spring (8) sleeved on the piston rod.

6. The pneumatic stop valve according to claim 5, characterized in that: The spring is a cylindrical helical compression spring, one end of which is supported by the piston (6) and the other end of which is supported by the baffle (9).

7. The pneumatic stop valve according to claim 5, characterized in that: The third sealing element (7) is an O-ring installed on the outer periphery of the piston (6).

8. The pneumatic stop valve according to claim 5, characterized in that: The bottom of the piston sleeve (3) abuts against the top of the valve tube (2), and the piston sleeve and the valve tube are locked and connected to each other via screws (4).

9. The pneumatic stop valve according to claim 5, characterized in that: The valve stem (10) and the piston rod are constructed as one piece.

10. The pneumatic stop valve according to claim 1, characterized in that: The protrusion of the valve tube (2) is cylindrical and has an external thread on its outer circumferential surface, and the groove of the valve seat body (1) is circular hole-shaped and has an internal thread matching the external thread on its inner circumferential surface.

11. The pneumatic stop valve according to claim 1, characterized in that: The side wall of the first counterbore has a channel communicating with the fluid inlet, and the bottom surface of the first counterbore has a channel communicating with the fluid outlet.

12. The pneumatic stop valve according to claim 1, characterized in that: The shaft shoulder has a groove portion for accommodating the second sealing element (11) on its side facing the second counterbore bottom surface.

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