CN212480143U - Pneumatic stop valve - Google Patents

Abstract

The utility model relates to a pneumatic stop valve, it includes valve seat portion, case portion and pneumatic executive portion. According to the invention, a first chamber is formed in the fluid passage of the valve seat body, which first chamber is delimited jointly by the valve seat body and the valve stem and is provided with a first sealing element which acts when the valve stem is moved to close the fluid passage, in order to sealingly isolate the fluid inlet from the fluid outlet; a second chamber is formed in the valve tube of the valve core part, which is delimited jointly by the valve tube and the valve rod and is provided with a second sealing element that acts when the valve rod moves to open the fluid channel, in order to sealingly isolate the valve seat part from the valve tube of the valve core part. Through the utility model discloses the small-size gas drive high pressure stop valve of this kind that realizes simple structure, cost are lower, and are applicable to scientific research institution or laboratory very much.

Description

Pneumatic stop valve

Technical Field

The utility model relates to a valve control technical field. Particularly, the utility model relates to a pneumatic stop valve, especially be fit for scientific research institution or laboratory in the middle of the small-size high-pressure pneumatic stop valve of using of high-pressure fluid control.

Background

Valves are the main control components in fluid delivery or gas-tight detection systems, with high-pressure shut-off valves being one of the more widely used types of valves. At present, the small-sized high-pressure stop valve is mainly controlled by hand, the control precision is not high, and the automation is difficult to realize. A small number of high-pressure pneumatic stop valve products exist in the market, but the high-pressure pneumatic stop valve products are not suitable for being applied to scientific research institutions or laboratories due to complex structures, easy damage and large volumes.

SUMMERY OF THE UTILITY MODEL

An object of the utility model is to develop a pneumatic stop valve, especially be fit for scientific research institution or laboratory in the middle of the small-size high-pressure pneumatic stop valve of using of high-pressure fluid control, optimize the structural design of valve to satisfy the market demand of this type of product.

Therefore, the utility model provides a pneumatic stop valve, it includes:

a valve seat portion having a valve seat main body with a fluid inlet and a fluid outlet and a fluid passage connecting the fluid inlet and the fluid outlet;

a spool portion connected to the valve seat portion and including a valve tube and a valve rod protruding from the valve tube toward the valve seat main body, the valve rod being capable of reciprocating within a guide hole of the valve tube; and

a pneumatic actuator configured as a piston-type driving mechanism having a piston rod connected to the valve rod and capable of driving the valve rod to reciprocate by the piston rod to close or open the fluid passage;

wherein a first chamber is configured in the fluid passage of the valve seat body, the first chamber being defined by the valve seat body and the valve stem together, the first chamber being provided with a first sealing element acting between the valve seat body and the valve stem when the valve stem moves to close the fluid passage to sealingly isolate the fluid inlet from the fluid outlet; at the connection point of the seat part and the valve body, a second chamber is formed in the valve tube of the valve body, which second chamber is delimited jointly by the valve tube and the valve rod, and the second chamber is provided with a second sealing element which acts between the valve tube and the valve rod when the valve rod moves to open the fluid channel, in order to sealingly isolate the seat part from the valve tube of the valve body.

According to the utility model discloses, through the local structure of rational arrangement case portion (especially valve rod) and disk seat portion (especially disk seat main part) for the open and close of valve is controlled and is coordinated the linkage with sealed effect, allows to realize its miniaturized design when guaranteeing that the valve function is reliable.

Provision is preferably made here for: the valve body part is coaxially arranged with the valve seat part and the pneumatic execution part along the axial direction of the valve rod, one end of the valve rod extends into the valve seat main body, and the other end of the valve rod is connected with a piston rod of the piston type driving mechanism, wherein the first sealing element and the second sealing element are respectively subjected to axial acting pressure when the valve rod moves axially to close or open the fluid channel. In this way, the valve as a whole has a compact design, while at the same time it is particularly advantageous that the axial forces that operate the opening and closing movement of the valve stem can be fully utilized for performing the sealing function.

Advantageously, the first sealing element and the second sealing element are elastomer seals which produce a corresponding sealing isolation when subjected to axially acting pressure forces. The elastomeric seal is suitably an O-ring seal. Therefore, in the technical scheme provided by the utility model, sealing element can directly choose for use general standard component as the sealing washer to show manufacturing, use and the maintenance cost that reduces the product.

According to some embodiments of the utility model, piston actuating mechanism includes the piston cover and can be in this piston cover reciprocating motion's piston, the piston cover is equipped with air source interface at the top, closed through the baffle in the bottom, the piston rod is connected in the piston lower part and is passed the baffle and link to each other with the valve rod, be equipped with third sealing element between piston outer peripheral face and piston cover internal face, thereby form upper and lower two cavity of sealed isolation each other inside the piston cover, wherein, go up cavity and air source interface intercommunication, the internal spring of arranging in the piston rod that is equipped with of cavity of resorption. Here, air source interface can be connected to outside compressed air source, adjusts through outside air supply, the utility model discloses a pneumatic stop valve can be used to the circulation pressure and reaches 60 MPa's various application. The spring then returns the valve stem to the normal position when the air supply is turned off, while advantageously being applied to apply the pressure required for sealing.

Here, the spring may be a cylindrical helical compression spring, one end of which is supported by the piston and the other end of which is supported by the damper. The cylindrical helical compression spring can be directly selected from universal standard parts. The spring may be mounted in place with appropriate pre-tensioning taking into account the fluid working pressure and/or the pneumatic operating pressure of the valve.

Here, the third seal member is preferably an O-ring seal attached to the outer periphery of the piston.

In this case, the piston sleeve bottom rests against the valve tube top and can be screwed to the piston sleeve and the valve tube.

Advantageously, the valve rod is formed in one piece with the piston rod. In this way, a compact and compact design of the product and a reduced number of components can be achieved while ensuring a reliable force transmission of the actuating member.

According to some embodiments of the utility model, the valve pipe bottom is formed with the arch, and the disk seat main part has the recess that corresponds with this arch, the arch with the recess cooperation is connected and makes the installation of case portion be fixed in disk seat portion.

Here, it is possible that the projection of the valve tube has a cylindrical shape and has an external thread on an outer circumferential surface thereof, and the recess of the valve seat body has a circular hole shape and has an internal thread on an inner circumferential surface thereof that is matched with the external thread. Therefore, the valve pipe (or the valve core part) can be screwed with the valve seat main body (or the valve seat part) through threads, and simple and reliable assembly and fixation of the valve pipe (or the valve core part) and the valve seat main body (or the valve seat part) are realized.

Regarding first cavity and sealing design thereof, according to the utility model discloses a concrete implementation form, the disk seat main part is in the tank bottom of recess has first counter bore, and the valve rod tip stretches into in the first counter bore, the terminal surface of valve rod with first counter bore delimits jointly first cavity, first sealing element settle in first counter bore bottom surface and receive the extrusion when valve rod axial motion in order to close fluid passage between valve rod terminal surface and first counter bore bottom surface. A simple and reliable end-face seal can thus advantageously be achieved, which sealingly isolates the fluid inlet from the fluid outlet.

Here, it is preferable that the side wall of the first counterbore has an orifice communicating with the fluid inlet, and the bottom surface of the first counterbore has an orifice communicating with the fluid outlet. The utility model discloses an within the scope, according to concrete needs and installation condition, the fluid advances, the setting position of export and the arrangement and the trend in pore can take various different design forms, as long as keep their connection and functional relation unchangeable.

Regarding the second chamber and its sealing design, according to a specific embodiment of the present invention, the valve tube is in the raised end face has a second counter bore, the second counter bore axially adjoins the guide hole of the valve tube, the valve stem is configured with a radially protruding shoulder at a position adjoining the end thereof that protrudes into the valve seat body, the valve stem passes through the shoulder and the second counter bore jointly delimit the second chamber, a second sealing element is disposed on one side of the shoulder facing the bottom surface of the second counter bore and is pressed between the shoulder and the bottom surface of the second counter bore when the valve stem moves axially to open the fluid passage. This advantageously makes it possible to achieve a simple and reliable end-face seal, which sealingly isolates the valve seat (i.e. the fluid medium side) from the valve tube of the valve core (i.e. the actuating element side).

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 counterbore bottom face.

The utility model discloses a pneumatic stop valve can construct for small-size high-pressure pneumatic stop valve, and the circulation of high-pressure gas or liquid in the process line of small-bore in the scientific research institution laboratory, closing control are particularly useful for. In particular, the technical solution proposed in the present application can achieve at least one of the following advantageous technical effects:

(1) the whole structure is simple and compact, and the volume is small;

(2) the movable parts are few, and are not easy to damage;

(3) the manufacture and the assembly are simple, and the cost is low;

(4) the design and control parameters are few, the modification and the reconstruction are easy, and the product series expansion is realized;

(5) the sealing mechanism (especially the end plane sealing mode) has simple structure, reliable function and low cost;

(6) the highest flow pressure can reach 60MPa, and the valve can be widely suitable for various application occasions.

Drawings

In which some exemplary embodiments of the invention are shown. The embodiments and figures disclosed herein are to be regarded as illustrative rather than restrictive. It is also noted that for purposes of clarity of illustration, certain features are not necessarily drawn to scale in the drawings.

FIG. 1 is a schematic structural view of a preferred embodiment of the pneumatic stop valve of the present invention;

FIG. 2 is a schematic diagram of the operation of the preferred embodiment of the pneumatic shut-off valve of FIG. 1, wherein the valve is in a closed position;

fig. 3 is a schematic diagram of the operation of the preferred embodiment of the pneumatic shut-off valve of fig. 1, wherein the valve is in an open state.

In the drawings: 100. the valve comprises a valve seat portion, a valve core portion, a pneumatic execution portion 300, a valve seat main body 1, a valve pipe 2, a piston sleeve 3, a screw 4, an air source interface 5, a piston 6, a third sealing element 7, a spring 8, a baffle plate 9, a valve rod 10, a second sealing element 11, a first sealing element 12, a first chamber S1, a second chamber S2, a first chamber

Detailed Description

The technical solution of the embodiment of the present invention will be described below with reference to the accompanying drawings. It is clear that the described embodiments relate only to a part of the embodiments of the invention, and not to all embodiments. Based on the embodiments disclosed in the present application, all other embodiments obtained by a person skilled in the art without making creative efforts belong to the protection scope of the present application.

The terms "first," "second," "third," and the like in the description and in the claims of the present application are used for distinguishing between different objects and not for describing a particular order. Furthermore, the terms "comprising" and "having," as well as any variant thereof, are intended to cover a non-exclusive inclusion. For example, a process, method, article, or apparatus that comprises a list of steps or elements is not limited to only those steps or elements but may alternatively include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus. It will be understood by those skilled in the art that throughout the present specification and claims, certain terms such as "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "axial", "radial", "circumferential", and the like, may be used in a given orientation or positional relationship indicated in the drawings for ease of description and simplicity of description only, and do not indicate or imply that the device, mechanism, structure, or element so referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus should not be considered as limiting the present invention.

Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one implementation of the invention. The appearances of the phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. It is explicitly and implicitly understood by one skilled in the art that the embodiments described herein can be combined with other embodiments.

Fig. 1 is a schematic structural diagram of a preferred embodiment of the pneumatic stop valve of the present invention. The utility model provides a pneumatic stop valve, it includes: a valve seat portion 100 having a valve seat main body 1 with a fluid inlet and a fluid outlet and a fluid passage connecting the fluid inlet and the fluid outlet; a spool portion 200 connected to the valve seat portion and including a valve tube 2 and a valve stem 10 protruding from the valve tube toward the valve seat main body, the valve stem being capable of reciprocating within a guide hole of the valve tube; and a pneumatic actuator 300 configured as a piston type driving mechanism having a piston rod connected to the valve stem 10 and capable of reciprocating the valve stem by the piston rod to close or open the fluid passage. According to the invention, a first chamber S1 is formed in the fluid passage of the valve seat body 1, which is delimited jointly by the valve seat body 1 and the valve rod 10, said first chamber being provided with a first sealing element 12 which acts between the valve seat body 1 and the valve rod 10 when the valve rod is moved to close the fluid passage, in order to sealingly isolate the fluid inlet from the fluid outlet; at the connection point of the valve seat and the valve body, a second chamber S2 is formed in the valve tube 2 of the valve body 200, which is delimited jointly by the valve tube 2 and the valve rod 10, and is provided with a second sealing element 11 that acts between the valve tube 2 and the valve rod 10 when the valve rod moves to open a fluid passage, in order to sealingly isolate the valve seat 100 from the valve tube 2 of the valve body 200.

According to the utility model discloses, through the local structure of rational arrangement case portion (especially valve rod) and disk seat portion (especially disk seat main part) for the open and close of valve is controlled and is coordinated the linkage with sealed effect, allows to realize its miniaturized design when guaranteeing that the valve function is reliable.

As shown in fig. 1, the valve core portion 200 is coaxially arranged with the valve seat portion 100 and with the pneumatic actuator 300 along the axial direction of the valve stem 10, one end of the valve stem 10 extends into the valve seat main body 1, and the other end is connected with the piston rod of the piston type driving mechanism, wherein the first sealing element 12 and the second sealing element 11 are respectively subjected to axially acting pressure when the valve stem moves axially to close or open the fluid passage. In this way, the valve as a whole has a compact design, while at the same time it is particularly advantageous that the axial forces that operate the opening and closing movement of the valve stem can be fully utilized for performing the sealing function. In this way, the valve as a whole has a compact design, while at the same time it is particularly advantageous that the axial forces that operate the opening and closing movement of the valve stem can be fully utilized for performing the sealing function.

Advantageously, according to the invention, the first sealing element 12 and the second sealing element 11 are elastomer seals which, when subjected to an axially acting pressure, produce a corresponding sealing and isolating effect. The elastomeric seal is preferably an O-ring seal.

According to the utility model discloses, as shown in fig. 1, piston actuating mechanism includes piston housing 3 and piston 6 that can be at this piston housing reciprocating motion, piston housing 3 is equipped with air source interface 5 at the top, closed through baffle 9 in the bottom, the piston rod is connected in piston 6 lower part and is passed baffle 9 and valve rod 10 and link to each other, be equipped with third sealing element 7 between piston outer peripheral face and piston housing internal face, thereby form upper and lower two cavity of sealed isolation each other in piston housing inside, wherein, go up cavity and air source interface intercommunication, be equipped with the spring 8 of cover on the piston rod in the cavity of resorption. Here, air source interface can be connected to outside compressed air source, adjusts through outside air supply, the utility model discloses a pneumatic stop valve can be used to the circulation pressure and reaches 60 MPa's various application. The spring then returns the valve stem to the normal position when the air supply is turned off, while advantageously being applied 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 of which is supported by the baffle 9. The spring may be mounted in place with appropriate pre-tension taking into account the fluid working pressure and/or the pneumatic operating pressure of the valve. The third sealing element 7 is preferably an O-ring seal mounted on the outer periphery of the piston 6.

As shown in fig. 1, the piston sleeve 3 rests at the bottom against the top of the valve tube 2 and is connected to the latter by means of screws 4.

According to the invention, it is particularly advantageous if the valve rod 10 is constructed in one piece with the piston rod. In this way, a compact and compact design of the product and a reduced number of components can be achieved while ensuring a reliable force transmission of the actuating member.

As shown in fig. 1, a protrusion is formed at the bottom of the valve pipe 2, and the valve seat body 1 has a groove corresponding to the protrusion, and the protrusion is engaged with the groove to fix the valve core 200 to the valve seat 100. Preferably, the protrusion of the valve tube 2 is cylindrical and has an external thread on its outer circumferential surface, and the recess of the valve seat body 1 is circular and has an internal thread on its inner circumferential surface that matches the external thread. Therefore, the valve pipe (or the valve core part) can be screwed with the valve seat main body (or the valve seat part) through threads, and the simple and reliable assembly and fixation of the valve pipe (or the valve core part) and the valve seat main body (or the valve seat part) are realized.

Regarding the first chamber S1 and its sealing design in the present invention, as shown in fig. 1, the valve seat body 1 is that the groove bottom of the groove has a first counter bore, the end of the valve rod 10 extends into the first counter bore, the end surface of the valve rod 10 and the first counter bore jointly define the first chamber S1, the first sealing element 12 is disposed on the bottom surface of the first counter bore and is squeezed between the end surface of the valve rod and the bottom surface of the first counter bore when the valve rod moves axially to close the fluid passage. A simple and reliable end-face seal can thus advantageously be achieved, which sealingly isolates the fluid inlet from the fluid outlet. Preferably, the side wall of the first counterbore has an orifice communicating with the fluid inlet, and the bottom surface of the first counterbore has an orifice communicating with the fluid outlet.

Of course, the design of the fluid inlet, outlet and communication ports in the valve seat body is not limited to the specific manner described or illustrated. The utility model discloses an within the scope, according to concrete needs and installation condition, the fluid advances, the setting position of export and the arrangement and the trend in pore can take various different design forms, as long as keep their connection and functional relation unchangeable.

Regarding the second chamber S2 and its sealing design in the present invention, as shown in fig. 1, the valve tube 2 is that the raised end face has a second counter bore, the second counter bore axially adjoins to the guide hole of the valve tube, the valve stem 10 is configured with a radially protruding shoulder at the position adjoining to the end of the valve stem that extends into the valve seat body, the valve stem passes through the shoulder and the second counter bore jointly define the second chamber S2, the second sealing element 11 is disposed on the side of the shoulder facing the bottom surface of the second counter bore and is pressed between the shoulder and the bottom surface of the second counter bore when the valve stem moves axially to open the fluid passage. This advantageously makes it possible to achieve a simple and reliable end-face seal, which sealingly isolates the valve seat (i.e. the fluid medium side) from the valve tube of the valve core (i.e. the actuating element side). Preferably, the shoulder has a groove for seating the second sealing element 11 on its side facing the second counterbore bottom face.

FIG. 2 is a schematic diagram of the operation of the preferred embodiment of the pneumatic shut-off valve of FIG. 1, wherein the valve is in a closed position; fig. 3 is a schematic diagram of the operation of the preferred embodiment of the pneumatic shut-off valve of fig. 1, wherein the valve is in an open state. The access of high pressure fluid (gas or liquid) is indicated by the open arrows in fig. 2 and 3. The utility model discloses a pneumatic stop valve accessible realizes opening and close of valve and controls as follows:

when an external air source is connected, the piston 6 is driven to compress the spring 8, the piston rod/valve rod 10 is driven to move downwards, the bottom end face of the valve rod extrudes a sealing ring on the bottom surface of the counter bore of the valve seat, a fluid channel in the valve seat main body 1 is stopped, and the valve is in a closed state;

when an external air source is turned off, the piston 6 is reset under the action of the rebounding restoring force of the spring 8, the piston rod/valve rod 10 is driven to move upwards, the sealing ring between the valve rod 10 and the valve pipe 2 generates a sealing effect, at the moment, the fluid channel is opened, and the valve is in an opening state.

A new type of small pneumatic high-pressure stop valve can thus be realized, which is shown in fig. 1 and comprises a valve seat body 1, a valve rod 10, a valve tube 2, a piston 6, a piston sleeve 3, a spring 8, a seal ring a (i.e., a third sealing element 7), a seal ring B (i.e., a second sealing element 11), a seal ring C (i.e., a first sealing element 12), an air source interface 5, and a screw 4. The valve seat main body 1 is connected with the valve pipe 2 through threads, two ends of the valve seat main body 1 are fluid inlet and outlet ports, a sealing counter bore is arranged at the connecting part of the middle of the valve seat main body 1 and the valve pipe 2, the bottom of the sealing counter bore is communicated with the fluid inlet and outlet, and a sealing ring C (namely a first sealing element 12) is arranged at the bottom of the counter bore of the valve seat main body 1; the valve rod 10 is connected with the upper piston 6 through a central hole of the valve pipe 2, a baffle plate 9 and a spring 8, and a sealing ring B (namely a second sealing element 11) is arranged on the T-shaped back of the bottom end area of the valve rod 10; the piston 6 connected with the valve rod 10 is arranged in the piston sleeve 3, a sealing ring A (namely a third sealing element 7) is arranged between the piston and the piston sleeve 3, and the top of the piston sleeve 3 is provided with a driving air source interface 5 to form an air driving piston mechanism. The piston sleeve 3 and the valve pipe 2 are tightly connected by a screw(s) 4.

The packing B (i.e., the second sealing member 11) provided between the valve stem 10 and the valve tube 2 functions to hermetically isolate the valve seat portion from the valve tube of the valve core portion when the valve stem moves to open the fluid passage.

The sealing ring C (i.e., the first sealing member 12) provided between the valve stem 10 and the valve seat body 1 functions to hermetically isolate the fluid inlet from the fluid outlet when the valve stem is moved to close the fluid passage.

The working principle of the small pneumatic high-pressure stop valve is as follows:

referring to fig. 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 that the air source drives the piston 6 to compress the spring 8, the valve rod 10 is driven to move downwards, the bottom end face of the valve rod 10 presses the sealing ring C on the bottom face of the counter bore of the valve seat, the fluid passage in the valve seat main body 1 is cut off, and the valve is set in a closed state;

referring to fig. 3, when the external air source is turned off, the spring pressure P2 on the piston 6 is greater than the external air source pressure P1(P1 is equal to 0), so that the spring 8 rebounds to push the piston 6 and drive the valve rod 10 to move upward, so that the sealing ring B arranged on the back of the T-shaped portion of the bottom end area of the valve rod is attached to the bottom surface of the valve tube counter bore, and the sealing ring B is further pressed against the bottom surface of the valve tube counter bore due to the acting force applied to the bottom of the valve rod by the high-pressure fluid, so that the sealing effect is enhanced, at this time, the fluid passage in the valve seat body 1 is opened, and the valve is.

It should be noted that within the framework of the present invention, the pneumatic shut-off valve can be of the straight-through, straight-through and right-angled type, without being limited to the specific case described/illustrated, for which only the orientation of the fluid inlet and outlet and the arrangement and orientation of the ducts need to be designed accordingly. Furthermore, the utility model discloses a pneumatic stop valve not only can design for normally open type, also can consider to design for normally closed type, for this reason need the pneumatic execution portion of corresponding adaptation, for example can exchange piston actuating mechanism's power gas chamber and spring action chamber each other.

The above description of the embodiments is only intended to help understand the core idea of the present invention. It will, of course, be understood by those skilled in the art that various modifications and additions may be made to the specific embodiments described, or substituted in a similar manner, without departing from the spirit of the invention or exceeding the scope thereof as defined in the appended claims.

Claims (15)

1. A pneumatic shut-off valve comprising:

a valve seat portion (100) having a valve seat main body (1) with a fluid inlet and a fluid outlet and a fluid passage connecting the fluid inlet and the fluid outlet;

a spool portion (200) connected with the valve seat portion and including a valve tube (2) and a valve rod (10) protruding from the valve tube toward the valve seat main body, the valve rod being capable of reciprocating within a guide hole of the valve tube; and

a pneumatic actuator (300) configured as a piston-type drive mechanism having a piston rod connected to the valve stem (10) and capable of reciprocating to close or open the fluid passage by driving the valve stem by the piston rod;

characterized in that a first chamber (S1) is configured in the fluid passage of the valve seat body (1), which is delimited jointly by the valve seat body (1) and the valve stem (10), said first chamber being provided with a first sealing element (12) acting between the valve seat body (1) and the valve stem (10) when the valve stem moves to close the fluid passage, to sealingly isolate the fluid inlet from the fluid outlet; at the connection point of the seat part and the valve body part, a second chamber (S2) is formed in the valve tube (2) of the valve body part (200), which is delimited jointly by the valve tube (2) and the valve rod (10), and is equipped with a second sealing element (11) that acts between the valve tube (2) and the valve rod (10) when the valve rod moves to open a fluid passage, in order to sealingly isolate the seat part (100) from the valve tube (2) of the valve body part (200).

2. The pneumatic shut-off valve according to claim 1, wherein, in the axial direction of the valve stem (10), the valve core portion (200) is arranged coaxially with the valve seat portion (100) and with the pneumatic actuator (300), and the valve stem (10) has one end protruding into the valve seat body (1) and the other end connected with a piston rod of the piston drive mechanism, wherein the first seal element (12) and the second seal element (11) are subjected to axially acting pressure when the valve stem is moved axially to close or open the fluid passage, respectively.

3. Pneumatic shut-off valve according to claim 2, characterised in that the first sealing element (12) and the second sealing element (11) are elastomer seals which produce a corresponding sealing isolation action in the event of an axially acting pressure.

4. The pneumatic shut-off valve of claim 3, wherein the elastomeric seal is an O-ring seal.

5. The pneumatic stop valve according to claim 1, wherein the piston-type driving mechanism comprises a piston sleeve (3) and a piston (6) which can reciprocate in the piston sleeve, the piston sleeve (3) is provided with an air source interface (5) at the top and is closed at the bottom by a baffle plate (9), the piston rod is connected to the lower part of the piston (6) and is connected with a valve rod (10) through the baffle plate (9), a third sealing element (7) is arranged between the outer peripheral surface of the piston and the inner wall surface of the piston sleeve, so that an upper cavity and a lower cavity which are sealed and isolated from each other are formed in the piston sleeve, wherein the upper cavity is communicated with the air source interface, and a spring (8) sleeved on the piston rod is arranged in the lower cavity.

6. Pneumatic stop valve according to claim 5, characterized in that the spring is a cylindrical helical compression spring, one end of which is supported on the piston (6) and the other end of which is supported on the stop plate (9).

7. Pneumatic shut-off valve according to claim 5, characterised in that the third sealing element (7) is an O-ring seal fitted to the outer periphery of the piston (6).

8. Pneumatic shut-off valve according to claim 5, characterised in that the piston sleeve (3) rests at its bottom against the top of the valve tube (2) and is lockingly connected to each other by means of screws (4).

9. Pneumatic shut-off valve according to claim 5, characterised in that the valve stem (10) is constructed in one piece with the piston rod.

10. The pneumatic stop valve according to any one of claims 1 to 9, wherein a protrusion is formed at the bottom of the valve tube (2), the valve seat body (1) has a groove corresponding to the protrusion, and the protrusion is engaged with the groove to fix the spool portion (200) to the valve seat portion (100).

11. Pneumatic stop valve according to claim 10, characterized in that the projection of the valve tube (2) is cylindrical and has an external thread on its outer circumference, and the recess of the valve seat body (1) is circular-hole-shaped and has an internal thread on its inner circumference, which fits the external thread.

12. The pneumatic stop valve according to claim 10, characterized in that the valve seat body (1) has a first counter bore at the bottom of the groove, into which the end of the valve stem (10) protrudes, the end face of the valve stem (10) and the first counter bore together delimiting the first chamber (S1), the first sealing element (12) being seated in the first counter bore bottom face and being pressed between the valve stem end face and the first counter bore bottom face when the valve stem is moved axially to close the fluid passage.

13. The pneumatic shut-off valve of claim 12, wherein the side wall of the first counterbore has an orifice in communication with the fluid inlet, and the bottom surface of the first counterbore has an orifice in communication with the fluid outlet.

14. Pneumatic stop valve according to claim 10, characterised in that the valve tube (2) has, at the end face of the projection, a second counter bore which axially adjoins the guide bore of the valve tube, the valve stem (10) being configured with a radially projecting shoulder adjoining its end projecting into the valve seat body, the valve stem delimiting the second chamber (S2) jointly with the second counter bore by means of the shoulder, the second sealing element (11) being arranged on the side of the shoulder facing the bottom face of the second counter bore and being pressed between the shoulder and the bottom face of the second counter bore when the valve stem is moved axially to open the fluid passage.

15. Pneumatic shut-off valve according to claim 14, characterised in that the shoulder has a groove for seating the second sealing element (11) on its side facing the second counterbore bottom face.

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