CN218523079U

CN218523079U - Low-temperature anti-flutter one-way valve structure

Info

Publication number: CN218523079U
Application number: CN202221862153.3U
Authority: CN
Inventors: 王喜良
Original assignee: Landspace Technology Co Ltd
Current assignee: Landspace Technology Co Ltd
Priority date: 2022-07-19
Filing date: 2022-07-19
Publication date: 2023-02-24
Anticipated expiration: 2032-07-19

Abstract

The utility model provides a low temperature prevents check valve structure that shimmys contains entry casing, export casing, case, uide bushing, spring holder and spring. The inlet shell and the outlet shell are respectively provided with a first channel and a second channel; the action area of the guide sleeve and the valve core, which is acted by inflow medium towards the outlet shell side, is larger than the action area of the spring seat, which is acted by return medium towards the inlet shell side; the valve core and the guide sleeve are both positioned in the inlet shell, one end of the valve core is positioned in the guide sleeve, the other end of the valve core is communicated with the inlet end of the inlet shell, one part of the outer wall of the guide sleeve is tightly attached to the inner wall of the inlet shell, the other part of the outer wall of the guide sleeve is tightly attached to the inner wall of the outlet shell, and the guide sleeve is movably arranged in the inlet shell and the outlet shell. The check valve can avoid flutter of the valve body, and improves working performance and reliability of the valve.

Description

Low-temperature anti-flutter one-way valve structure

Technical Field

The utility model relates to a driving system valve technical field especially relates to a check valve structure that quivers is prevented to low temperature.

Background

With the rapid development of the aerospace industry, all the technologies related to the rocket field also realize the rapid advance. The check valve is an important component of a self-generated pressurizing conveying system of the carrier rocket engine and plays an important role in a pressurizing path. In the performance test, the one-way valve generates the flutter phenomenon for many times. When the engine works under a low working condition, the medium flow is small, the problem of flutter is easily caused due to the low inlet and outlet pressure, the normal work of a pressurization/blowing system is influenced, and the self function failure of a valve or the instability of the state of the pressurization blowing system can be caused in serious conditions.

At present, there are several improved structures for the problem of check valve flutter, such as adding a bush through a valve core, and avoiding flutter by adding a stainless steel spring ring or a corrugated band piston ring to increase a damping structure. However, these methods have problems, for example, the use of the bush and the stainless steel spring ring is prone to generate surplus or seizing, and the use of the corrugated band piston ring has unstable damping effect at normal and low temperatures.

It is needed to provide a check valve which can be applied to low-temperature environment, avoid valve body flutter in the working process and improve the working performance and reliability of the valve.

Disclosure of Invention

An object of the utility model is to overcome prior art not enough, provide a low temperature prevents check valve structure that shimmys. The valve structure can be suitable for low-temperature environment, avoids valve body flutter in the working process, and improves the working performance and reliability of the valve, thereby improving the working reliability and efficiency of the liquid rocket engine.

An aspect of the utility model provides a low temperature prevents check valve structure that shimmys contains entry casing, export casing, case, uide bushing, spring holder and spring. The inlet shell and the outlet shell are respectively provided with a first channel and a second channel which are communicated with each other, and the inlet end of the outlet shell is screwed into the outlet end of the inlet shell and then clings to the inner wall of the inlet shell; the action area of the guide sleeve and the valve core, which is acted by inflow medium towards the outlet shell side, is larger than the action area of the spring seat, which is acted by backflow medium towards the inlet shell side. The valve core and the guide sleeve are both positioned in the inlet shell, one end of the valve core is positioned in the guide sleeve and is fixedly connected with the inner wall of the guide sleeve, the other end of the valve core is communicated with the inlet end of the inlet shell, one part of the outer wall of the guide sleeve is tightly attached to the inner wall of the inlet shell, the other part of the outer wall of the guide sleeve is tightly attached to the inner wall of the outlet shell, and the guide sleeve is configured to be movable in the inlet shell and the outlet shell along the axial direction of the first channel. The valve core comprises a main channel and auxiliary channels, the auxiliary channels are uniformly distributed along the circumferential direction of the valve core, one end of each auxiliary channel is communicated with one end of the main channel, the other end of each auxiliary channel is communicated with the inlet end of the inlet shell, and the other end of each main channel is communicated with the second channel. The valve core is provided with a valve core, the valve core is provided with an outlet shell, the valve core is arranged in the outlet shell, the valve seat and the spring are both positioned in the outlet shell, the circumferential outer surface of the valve seat is tightly attached to the inner wall of the outlet shell, and the spring is used for being matched with the valve seat to generate acting force towards the direction of the inlet shell on the valve core.

When the medium entering the inlet shell end is reduced, the acting force of the valve core and the guide sleeve on the inlet shell side and towards the outlet shell is larger than the acting force of the spring seat on the outlet shell side and towards the inlet shell, so that the acting force of the spring seat on the valve core is at least partially counteracted, and the phenomenon that the valve core generates vibration is further reduced.

Furthermore, be located in the first passageway the uide bushing with be equipped with first sealing member between the entry shells inner wall, the uide bushing is the communicating cylinder structure in both ends, just the cylinder structure contains first cylinder and the second cylinder that the external diameter is different, first cylinder is located and is close to the entrance point of entry casing, the second cylinder is located and is close to export casing one side, first cylinder to second cylinder transition point forms and is used for injecing the first spacing platform of first sealing member.

Furthermore, a supporting sleeve for limiting the first sealing element is further arranged on the circumferential outer side of the guide sleeve, the inner side surface of the supporting sleeve is tightly attached to the guide sleeve, the outer side surface of the supporting sleeve is tightly attached to the inner wall of the inlet shell and can move along the inner wall of the inlet shell, and the end face, close to the first limiting table, of the supporting sleeve is tightly attached to the end face, close to one end of the supporting sleeve, of the first sealing element.

Furthermore, a first external thread is arranged on the outer surface of the valve core, and a first internal thread matched with the first external thread is arranged on the inner side surface of the guide sleeve; the inner surface of the support sleeve is provided with a second internal thread, and the outer surface of the guide sleeve and the coincident part of the support sleeve are provided with a second external thread matched with the second internal thread.

Further, in the direction from the inlet housing to the outlet housing, the first channel includes a first channel body and a second channel body which have different diameters and are communicated with each other, the aperture of the first channel body is larger than that of the second channel body, and a transition portion between the first channel body and the second channel body forms a second limiting table for limiting the guide sleeve to move to one side of the inlet housing.

Furthermore, a first annular groove is formed in the end face, close to one end of the inlet shell, of the valve core, and a second sealing piece is arranged in the first annular groove.

Furthermore, an annular bulge is further arranged on the end face of the valve core, which is close to one end of the inlet shell, and the annular bulge is located on the radial outer side of the first annular groove.

Further, the end face of the inlet end of the inlet housing is provided with an annular recess forming a seal with the annular protrusion.

Furthermore, a second annular groove is formed in the end face, close to one end of the valve core, of the spring seat, and a third sealing element is arranged in the second annular groove; and one end, far away from the inlet shell, of the spring seat is also provided with a third annular groove for limiting the spring, one end of the spring is positioned in the third annular groove, and the other end of the spring is abutted against the end face, close to one end of the inlet shell, of the outlet shell.

Furthermore, the entry casing with the export casing passes through threaded connection, the entry casing with still be equipped with the fourth sealing member between the export casing, the export casing is close to entry casing one end is equipped with the spacing platform of third, the entry casing is close to export casing one end is equipped with the spacing platform of fourth, fourth sealing member both sides terminal surface respectively with the mesa of the spacing platform of third with the mesa of the spacing platform of fourth pastes tightly.

The embodiment of the utility model provides a flutter check valve structure is prevented by entry casing, export casing, case, uide bushing, spring holder and spring set and is constituteed. When the medium entering the inlet shell end is reduced, the end face size of the valve core and the end face size of the guide sleeve close to the inlet shell end are larger than the end face size of the spring seat close to the outlet shell end, so that the acting force of the valve core on the inlet shell side towards the outlet shell is larger than the acting force of the valve core on the outlet shell side towards the inlet shell, the acting force of the spring seat on the valve core is at least partially counteracted, and the phenomenon that the valve core generates flutter is further reduced. The whole structure can be suitable for a low-temperature environment, the valve body is prevented from fluttering in the working process, the working performance and the reliability of the valve are improved, and therefore the working reliability and the working efficiency of the liquid rocket engine are improved.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of the specification of the invention, illustrate exemplary embodiments of the invention and together with the description, serve to explain the principles of the invention.

Fig. 1 is a schematic structural view of the closing of the check valve in the embodiment of the present invention;

fig. 2 is a schematic structural view of the opening of the check valve in the embodiment of the present invention;

fig. 3 is a schematic structural diagram of the valve element in the embodiment of the present invention.

Description of reference numerals:

1 inlet housing 2 outlet housing

3 valve core 4 guide sleeve

5 spring seat 6 spring

7 first channel 8 second channel

9 main channel 10 auxiliary channel

11 first seal 12 support sleeve

13 second seal 14 annular projection

15 annular recess 16 third seal

17 fourth seal

Detailed Description

Reference will now be made in detail to various exemplary embodiments of the invention, which should not be considered limiting of the invention, but rather should be understood to be a more detailed description of certain aspects, features and embodiments of the invention.

It will be apparent to those skilled in the art that various modifications and variations can be made in the embodiments of the present disclosure without departing from the scope or spirit of the disclosure. Other embodiments will be apparent to those skilled in the art from consideration of the specification. The specification and examples are exemplary only.

The applicant's studies have found that the problem of flutter has a significant negative impact on the check valve. The fluttering process of the check valve is generally a reciprocating process of the valve core and the spring. On one hand, the reciprocating motion of the spring can accelerate the fatigue failure of the spring, and meanwhile, the abrasion of the guide structure in the check valve is accelerated, so that the effective opening times of the check valve are reduced, and the service life of the check valve is shortened; on the other hand, the reciprocating motion of the valve core increases the impact frequency of the valve seat on the sealing material, accelerates the abrasion of the valve seat and the sealing material, and influences the leakage rate and the sealing of the one-way valve. Specific solutions are needed to solve the flutter problem of the check valve, so as to improve the working performance and reliability of the check valve.

One aspect of the utility model provides a low temperature prevents check valve structure that shimmys. As shown in fig. 1, 2 and 3, the check valve structure includes an inlet housing 1, an outlet housing 2, a spool 3, a guide sleeve 4, a spring seat 5 and a spring 6. The inlet housing 1 and the outlet housing 2 are respectively provided with a first channel 7 and a second channel 8 which are communicated with each other, and the inlet end of the outlet housing 2 is screwed into the outlet end of the inlet housing 1 and then is clung to the inner wall of the inlet housing 1. The area of the valve element 3 and the guide sleeve 4 that is acted upon by the inflowing medium toward the outlet housing 2 is larger than the area of the spring plate 5 that is acted upon by the returning medium toward the inlet housing 1. The valve core 3 and the guide sleeve 4 are both positioned in the inlet shell 1, one end of the valve core 3 is positioned in the guide sleeve 4 and is fixedly connected with the inner wall of the guide sleeve 4, the other end of the valve core is communicated with the inlet end of the inlet shell 1, one part of the outer wall of the guide sleeve 4 is tightly attached to the inner wall of the inlet shell 1, the other part of the outer wall of the guide sleeve 4 is tightly attached to the inner wall of the outlet shell 2, and the guide sleeve 4 is configured to be movable in the inlet shell 1 and the outlet shell 2 along the axial direction of the first channel 7. The valve core 3 comprises a main channel 9 and an auxiliary channel 10 (located at one side close to the inlet shell), the auxiliary channels 9 are uniformly distributed along the circumferential direction of the valve core 3, one end of each auxiliary channel is communicated with one end of the main channel 9, the other end of each auxiliary channel is communicated with the inlet end of the inlet shell 1, and the other end of the main channel 9 is communicated with the second channel 8. Spring holder 5 and spring 6 all are located export casing 2, and the circumference surface of spring holder 5 pastes closely with the inner wall of export casing 2, and spring 6 is used for cooperating with spring holder 5 in order to produce the effort to import casing 2 direction to case 3. When the medium entering from the inlet housing 1 end is reduced, the end face size of the valve core 3 and the end face size of the guide sleeve 4 close to the inlet housing 1 end are larger than the end face size of the spring seat 5 close to the outlet housing 2 end, so that the acting force of the valve core 3 on the inlet housing 1 side and towards the outlet housing 2 side is larger than the acting force of the valve core 3 on the outlet housing side and towards the inlet housing 1 side, the acting force of the spring seat 5 on the valve core 3 is at least partially offset, and the phenomenon that the valve core 3 generates vibration is further reduced.

Specifically, the embodiment of the utility model provides a low temperature check valve structure of preventing shimmying, when the medium that entry casing 1 end got into reduced, case 3 and uide bushing 4 were close to the end face dimensions of entry casing one end is greater than the end face dimensions that spring holder 5 was close to 2 one ends of export casing, makes case 3 be greater than the effort of case 3 orientation export casing 2 that the effort that the case 3 received in 2 sides of export casing in entry casing 1 side to make at least part offset the effort of spring holder 5 to case 3, and then reduce the phenomenon that case 3 produced shimmying. The whole structure of this application check valve can be applicable to low temperature environment, avoids the valve body to appear shimmying in the course of the work, improves the working property and the reliability of valve to improve the reliability and the efficiency of liquid rocket engine work.

In order to avoid leakage of liquid or gaseous medium from the gap between the guide sleeve 4 and the inlet housing 1, for example, a first seal 11 is provided between the guide sleeve 4 located in the first channel 7 and the inner wall of the inlet housing 1. In order to fix the first sealing member 11 firmly and prevent the guide sleeve 4 and the first sealing member 11 from moving in a displacement manner, for example, the guide sleeve 4 is a cylindrical structure with two ends communicated with each other, and the cylindrical structure includes a first cylinder and a second cylinder with different outer diameters. The first cylinder is located near the inlet end of the inlet housing, the second cylinder is located near one side of the outlet housing, the outer diameter of the first main body is larger than that of the second main body, and a transition part of the first cylinder to the second cylinder forms a first limiting table used for limiting the first sealing element 11.

It is worth mentioning that in order to avoid the first sealing element 11 sliding on the surface of the guiding sleeve 4 (moving away from the first stop), for example, a supporting sleeve 12 for limiting the first sealing element 11 is further provided on the circumferential outer side of the guiding sleeve 4, the inner side surface of the supporting sleeve 12 is closely attached to the guiding sleeve 4, and the outer side surface is closely attached to the inner wall of the inlet housing 1 and can move along the inner wall of the inlet housing 1. The end surface of the supporting sleeve 12 close to the first limiting table and the end surface of the first sealing element 11 close to the supporting sleeve 12 are tightly attached to each other.

In addition, in order to ensure that the valve core 3 is tightly connected with the guide sleeve 4 and firmly fixed, for example, the outer surface of the valve core 3 is provided with a first external thread, and the inner side surface of the guide sleeve 4 is provided with a first internal thread matched with the first external thread. In order to ensure that the support sleeve 12 and the guide sleeve 4 are fixed firmly, the inner surface of the support sleeve 12 is provided with a second internal thread, and the position of the outer side surface of the guide sleeve 4, which is overlapped with the support sleeve 12, is provided with a second external thread matched with the second internal thread.

In addition, along the direction from the inlet housing to the outlet housing, the first channel 7 comprises a first channel body and a second channel body which have different diameters and are communicated with each other, the aperture of the first channel body is larger than that of the second channel body, and the transition part of the first channel body and the second channel body forms a second limit table for limiting the guide sleeve 4 to move towards one side of the inlet housing 1. When the valve core 3 moves towards one side of the inlet shell 1, the end face of one end, close to the inlet shell 1, of the guide sleeve 4 is tightly attached to the table face of the second limiting table, and then the valve core 3 can be limited (the guide sleeve 4 and the valve core 3 are connected together through threads and can move axially along the first channel).

It is particularly noted that, when the valve is closed, in order to prevent impurities from entering the valve, for example, as shown in fig. 1, the end surface of the valve core 3 near the inlet end of the inlet housing 1 is provided with a first annular groove. Be equipped with second sealing member 13 in the first annular groove, second sealing member 13 plays sealed effect (sealed for the first time) on the one hand, and on the other hand plays cushioning effect, avoids the case to take place direct contact and cause the damage near the terminal surface of the exit end of entry casing 1 and the entry casing 1 terminal surface that corresponds, helps the protection to the case for 3 safety of case, stable work.

In the present embodiment, in order to further prevent impurities from entering the valve, and ensure the cleanness of the interior of the valve body, for example, the end surface of the valve core 3 near the inlet end of the inlet housing 1 is further provided with an annular protrusion 14. The annular projection 14 is located radially outside the first annular groove, and the end face of the inlet end of the inlet housing 1 is provided with an annular recess 15 that forms a seal with the annular projection 14. The valve is sealed for the second time through the annular bulge 14 and the annular concave part 15, so that impurities are prevented from entering, and the sealing performance of the valve can be further improved.

In order to facilitate the flow of the liquid medium or the gas medium through the valve body, for example, the spring seat 5 is provided with a hole having the same diameter as the main passage 9.

Because the liquid oxygen methane propellant engine has higher working pressure, in order to prevent the valve core from being damaged by overlarge sealing specific pressure caused by overlarge outlet pressure, the end part of the valve core is provided with a limiting table. For example, the clearance between the annular protrusion 14 and the end face of the inlet housing 1 is 0.2mm, that is, when the non-metal indentation of the valve core is higher than 0.2mm, the annular protrusion on the valve core contacts with the annular concave part on the inlet housing, the roughness of the annular protrusion and the metal sealing surface of the inlet housing is less than Ra0.2, and the valve core and the inlet housing can form a metal sealing strip at the same time, thereby protecting the non-metal from being damaged due to high-pressure environment and prolonging the service life.

Specifically, in order to avoid leakage of liquid or gaseous medium from the gap between the spring seat 5 and the outlet housing 2, for example, the end surface of the spring seat 5 near the valve element 3 is provided with a second annular groove, and a third sealing element 16 is arranged in the second annular groove. For convenience of fixing the spring 6, the spring 6 applies pressure to the spring seat 5 quickly along the axial direction of the first passage, for example, a third annular groove used for limiting the spring 6 is further arranged at one end, away from the inlet housing 1, of the spring seat 5, one end of the spring 6 is located in the third annular groove, and the other end of the spring 6 abuts against the end face, close to one end of the inlet housing 1, of the outlet housing 2.

In addition, in order to make the inlet housing 1 and the outlet housing 2 tightly connected, the fixation is firm, for example, the inlet housing 1 and the outlet housing 2 are connected by screw threads. In order to avoid leakage of liquid or gaseous medium from the gap between the inlet housing 1 and the outlet housing 2, a fourth seal 17 is provided between the inlet housing 1 and the outlet housing 2, for example. Export casing 2 is close to 1 one end of entry casing and is equipped with the spacing platform of third, and entry casing 1 is close to 2 one end of export casing and is equipped with the spacing platform of fourth, the entry casing with export casing threaded connection back, the terminal surface in fourth sealing member 17 both ends pastes tightly with the mesa of the spacing platform of third and the mesa of the spacing platform of fourth respectively.

In the embodiment, the first sealing element and the third sealing element are of spring energy storage sealing ring structures, the second sealing element and the fourth sealing element are of low-temperature-resistant non-metal valve port sealing structures, and the check valve can be applied to the environment with the temperature of-196-100 ℃ and the high pressure of not higher than 70MPa, so that the working range and the sealing reliability are improved.

The foregoing is only an illustrative embodiment of the present invention, and any equivalent changes and modifications made by those skilled in the art without departing from the spirit and principles of the present invention should fall within the protection scope of the present invention.

Claims

1. A low-temperature anti-flutter one-way valve structure is characterized by comprising an inlet shell, an outlet shell, a valve core, a guide sleeve, a spring seat and a spring, wherein,

the inlet shell and the outlet shell are respectively provided with a first channel and a second channel which are communicated with each other, and the inlet end of the outlet shell is screwed into the outlet end of the inlet shell and then clings to the inner wall of the inlet shell; the action area of the guide sleeve and the valve core, which is acted by inflow medium towards the outlet shell side, is larger than the action area of the spring seat, which is acted by return medium towards the inlet shell side;

the valve core and the guide sleeve are both positioned in the inlet shell, one end of the valve core is positioned in the guide sleeve and is fixedly connected with the inner wall of the guide sleeve, the other end of the valve core is communicated with the inlet end of the inlet shell, one part of the outer wall of the guide sleeve is tightly attached to the inner wall of the inlet shell, the other part of the outer wall of the guide sleeve is tightly attached to the inner wall of the outlet shell, and the guide sleeve is configured to be movable in the inlet shell and the outlet shell along the axial direction of the first channel;

the valve core comprises a main channel and an auxiliary channel, the auxiliary channel is uniformly distributed along the circumferential direction of the valve core, one end of the auxiliary channel is communicated with one end of the main channel, the other end of the auxiliary channel is communicated with the inlet end of the inlet shell, and the other end of the main channel is communicated with the second channel;

the spring seat and the spring are both positioned in the outlet shell, the circumferential outer surface of the spring seat is tightly attached to the inner wall of the outlet shell, the spring is used for being matched with the spring seat to generate acting force towards the inlet shell to the valve core,

when the medium entering the inlet shell end is reduced, the acting force of the valve core and the guide sleeve on the inlet shell side towards the outlet shell is larger than the acting force of the spring seat on the outlet shell side towards the inlet shell, so that the acting force of the spring seat on the valve core is at least partially counteracted, and the phenomenon that the valve core generates vibration is further reduced.

2. The cryogenic flutter-proof check valve structure according to claim 1,

a first sealing element is arranged between the guide sleeve positioned in the first channel and the inner wall of the inlet shell; the uide bushing is the communicating cylinder structure in both ends, just the cylinder structure contains first cylinder and the second cylinder that the external diameter is different, first cylinder is located and is close to the entrance point of entry casing, the second cylinder is located and is close to export casing one side, first cylinder to second cylinder transition position forms and is used for injecing the first spacing platform of first sealing member.

3. The cryogenic flutter-proof check valve structure according to claim 2, wherein a support sleeve for limiting the first sealing element is further arranged on the circumferential outer side of the guide sleeve, the inner side surface of the support sleeve is tightly attached to the guide sleeve, the outer side surface of the support sleeve is tightly attached to the inner wall of the inlet shell and can move along the inner wall of the inlet shell, and the end surface of one end, close to the first limiting table, of the support sleeve is tightly attached to the end surface of one end, close to the support sleeve, of the first sealing element.

4. The cryogenic flutter-proof check valve structure according to claim 3, wherein a first external thread is arranged on the outer surface of the valve core, and a first internal thread matched with the first external thread is arranged on the inner side surface of the guide sleeve; the inner surface of the support sleeve is provided with a second internal thread, and the position of the outer side surface of the guide sleeve, which is overlapped with the support sleeve, is provided with a second external thread matched with the second internal thread.

5. The cryogenic flutter-proof check valve structure according to claim 1, wherein the first passage comprises a first passage body and a second passage body which have different diameters and are communicated with each other in sequence from the inlet housing to the outlet housing, the aperture of the first passage body is larger than that of the second passage body, and a transition portion of the first passage body and the second passage body forms a second limit stop for limiting the guide sleeve to move to one side of the inlet housing.

6. The cryogenic flutter-proof one-way valve structure according to claim 1, wherein an end face of the valve core, which is close to one end of the inlet housing, is provided with a first annular groove, and a second sealing element is arranged in the first annular groove.

7. The cryogenic flutter-proof one-way valve structure according to claim 6, wherein an end face of the valve core, which is close to one end of the inlet housing, is further provided with an annular protrusion, and the annular protrusion is located radially outside the first annular groove.

8. The cryogenic flutter resistant check valve structure of claim 7, wherein an end face of the inlet end of the inlet housing is provided with an annular recess that forms a seal with the annular protrusion.

9. The cryogenic flutter-proof check valve structure as claimed in claim 1,

a second annular groove is formed in the end face, close to one end of the valve core, of the spring seat, and a third sealing element is arranged in the second annular groove; and one end, far away from the inlet shell, of the spring seat is also provided with a third annular groove for limiting the spring, one end of the spring is positioned in the third annular groove, and the other end of the spring is abutted against the end face, close to one end of the inlet shell, of the outlet shell.

10. The cryogenic flutter-proof check valve structure according to claim 1, wherein the inlet housing and the outlet housing are connected through threads, and a fourth sealing member is further arranged between the inlet housing and the outlet housing; the outlet shell is close to one end of the inlet shell is provided with a third limiting table, the inlet shell is close to one end of the outlet shell is provided with a fourth limiting table, the inlet shell is in threaded connection with the outlet shell, and end faces of two ends of a fourth sealing element are respectively attached to the table top of the third limiting table and the table top of the fourth limiting table.