Protective net device and molecular pump

Abstract

The utility model provides a protective net device and a molecular pump. The protective net device comprises a mounting cylinder, a protective net, a first connecting rod, a second connecting rod, a third connecting rod, a fourth connecting rod and a fifth connecting rod, the first sieve plate is fixedly arranged at the first end and is provided with a plurality of first through holes; the second sieve plate is located on the side, close to the second end, of the first sieve plate, and is movably arranged in the mounting barrel in the central axis direction of the mounting barrel so as to be attached to or separated from the first sieve plate; a plurality of second through holes corresponding to the first through holes are distributed in the second sieve plate, the second through holes are smaller than the first through holes, a plurality of third through holes are distributed in gaps among the second through holes, the third through holes are larger than the second through holes, and the third through holes correspond to gaps among the first through holes. When the second sieve plate is separated from the first sieve plate, gas passes through the second sieve plate through the second through hole and the third through hole; during fitting, gas passes through the second sieve plate through the second through hole; the aperture of gas penetrating through the second sieve plate can be adjusted, and filtration of large-particle impurities is increased.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of molecular pumps, and in particular to a protective screen device and a molecular pump. BACKGROUND

[0002] In the process of solar cell panel production, a vacuum process chamber needs to be used. For example, the vacuum coating of a solar cell panel needs to be completed in a vacuum chamber. The vacuum process chamber generally uses a molecular pump to exhaust the air in the chamber to create a vacuum environment.

[0003] In related technologies, a filter screen plate is generally arranged at the air inlet end of a molecular pump. Since the pore size of the filter holes in the filter screen plate is fixed, in order to reduce the cleaning frequency of dust accumulation on the filter screen plate, the pore size of the filter holes is generally allowed to pass slightly larger particles of dust, thereby causing the molecular pump to easily jam after a long time of operation, affecting the service life of the molecular pump. CONTENT OF THE UTILITY MODEL

[0004] The present application provides a protective screen device and a molecular pump to solve the technical problem that the filter screen of a molecular pump in related technologies generally allows slightly larger particles of dust to pass through, which easily causes the molecular pump to jam, affecting the service life of the molecular pump.

[0005] To solve the above problems, the present application provides a protective screen device for a molecular pump, which comprises:

[0006] A mounting cylinder having opposite first and second ends, the second end being used to connect with the molecular pump;

[0007] A first sieve plate fixedly arranged at the first end, the first sieve plate being provided with a plurality of first through holes;

[0008] A second sieve plate located at one side of the first sieve plate close to the second end and movably arranged in the mounting cylinder along the central axis direction of the mounting cylinder to be attached to or separated from the first sieve plate; the second sieve plate is provided with a plurality of second through holes corresponding to the first through holes, the pore size of the second through holes being smaller than that of the first through holes, and the gaps between the plurality of second through holes being provided with a plurality of third through holes, the pore size of the third through holes being larger than that of the second through holes, and the gaps between the plurality of third through holes corresponding to the gaps between the plurality of first through holes.

[0009] In some embodiments, one side of the second sieve plate facing the first sieve plate is provided with a plurality of protrusions matched with the first through holes, the second through holes being formed on the protrusions, the protrusions being embedded in the first through holes when the second sieve plate is moved to be attached to the first sieve plate, and the protrusions being separated from the first through holes when the second sieve plate is moved to be separated from the first sieve plate.

[0010] In some embodiments, the first through hole is a tapered hole, the protrusion is a tapered protrusion, and the tapered hole and the tapered protrusion are both small-diameter ends at one end close to the first end.

[0011] In some embodiments, the second screen plate is movably arranged in the mounting cylinder by an elastic member, and the elastic member is arranged such that, when the gas pressure on the side of the second screen plate close to the first screen plate is greater than a specified value, the second screen plate can press the elastic member to separate from the first screen plate; and when the gas pressure on the side of the second screen plate close to the first screen plate is less than the specified value, the elastic member can press the second screen plate to adhere to the first screen plate.

[0012] In some embodiments, the protective net device further comprises:

[0013] A fixed plate is fixedly arranged in the mounting cylinder and located on the side of the second screen plate away from the first screen plate.

[0014] The side of the second screen plate close to the fixed plate is provided with a connecting rod, one end of the elastic member is connected to the connecting rod, and the other end is connected to the fixed plate.

[0015] In some embodiments, the connecting rod is arranged through the fixed plate, and the connecting rod is provided with a first limiting structure and a second limiting structure, the first limiting structure is located on the side of the fixed plate close to the second screen plate, and the second limiting structure is located on the side of the fixed plate away from the second screen plate.

[0016] In some embodiments, the fixed plate is distributed with a plurality of fourth through holes, and the diameter of the fourth through hole is smaller than the diameter of the second through hole.

[0017] In some embodiments, the protective net device further comprises:

[0018] A guide column is arranged along the moving direction of the second screen plate.

[0019] The second screen plate is provided with a guide groove matched with the guide column.

[0020] In some embodiments, the guide column is fixedly arranged on the inner wall of the mounting cylinder, and one end of the guide column abuts against the side of the first screen plate close to the second screen plate.

[0021] The application also provides a molecular pump, comprising:

[0022] A pump body having an air inlet and an air outlet.

[0023] Any protective screen device as described above is arranged in the pump body, and the second end is connected with the gas inlet.

[0024] The protective screen device provided by the application has the following beneficial effects: when the second end of the installation cylinder is connected to the gas inlet of the molecular pump, at the initial stage of starting the molecular pump, the gas flow is large, the second screen plate can be moved to the state of being separated from the first screen plate, at this time, the gas at the first end of the installation cylinder passes through the first through hole of the first screen plate first, and then passes through the second through hole and the third through hole of the second screen plate to enter the gas inlet of the molecular pump, so that the impact of the large gas flow on the protective screen device can be avoided; as the molecular pump operates, the gas flow decreases and the gas flow impact force decreases, the second screen plate can be moved to the state of being attached to the first screen plate, at this time, the third through hole of the second screen plate is closed by the first screen plate, and the gas at the first end of the installation cylinder only blows to the gas inlet of the molecular pump through the second through hole, so that the filtration of large particles in the air can be increased, the entry of large particles into the molecular pump can be reduced, the stable operation of the molecular pump can be ensured, and the service life of the molecular pump can be improved.

[0025] When the second screen plate is provided with protrusions matched with the first through holes, after the second screen plate is attached to the first screen plate, the protrusions are embedded in the first through holes, so that the first through holes can be prevented from being blocked by large particles in the process of filtering the gas by the protective screen device, and the cleaning frequency of the protective screen device during use can be reduced.

[0026] When the second screen plate is movably arranged in the installation cylinder by the elastic member, when the gas flow is large, the second screen plate can be separated from the first screen plate by extruding the elastic member under the action of the gas flow, as the gas flow decreases, the second screen plate can be attached to the first screen plate by the extrusion of the elastic member, so that the pore size of the second screen plate for the gas to pass through can be automatically adjusted by the protective screen device according to the gas flow. BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without any creative effort. Among them:

[0028] Figure 1 is a schematic diagram of the internal structure of the protective screen device provided by an embodiment of the application;

[0029] Figure 2 is a schematic diagram of the internal structure of the protective screen device provided by an embodiment of the application;

[0030] Figure 3 is a schematic diagram of the structure of the first screen plate and the second screen plate attached to each other in the protective screen device provided by an embodiment of the application;

[0031] Figure 4 is a schematic view of the internal structure of the protective net device provided by another embodiment of the present application;

[0032] Figure 5 is an exploded view of the protective net device from a first perspective provided by another embodiment of the present application;

[0033] Figure 6 is an exploded view of the protective net device from a second perspective provided by another embodiment of the present application;

[0034] Figure 7 is a schematic view of the structure in which the first screen plate and the second screen plate are attached in the protective net device provided by another embodiment of the present application;

[0035] Figure 8 is a schematic view of the structure in which the first screen plate and the second screen plate are separated in the protective net device provided by another embodiment of the present application;

[0036] Figure 9 is a schematic view of the structure in which the molecular pump is used to vacuum the cavity provided by an embodiment of the present application;

[0037] In the figure: 100, protective net device; 10, first screen plate; 11, first through hole; 20, second screen plate; 21, second through hole; 22, third through hole; 23, protrusion; 24, guide groove; 25, connecting rod; 251, first limiting structure; 252, second limiting structure; 30, mounting cylinder; 31, first end; 32, second end; 33, connecting flange; 40, fixed plate; 41, fourth through hole; 50, guide column; 60, elastic member; 200, pump body; 201, air inlet; 202, air outlet; 300, cavity. DETAILED DESCRIPTION

[0038] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. It can be understood that the specific embodiments described herein are only used to explain the present application, rather than limit the present application. In addition, it should be noted that, for the convenience of description, only the parts related to the present application are shown in the drawings, rather than all the structures. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0039] In the description of this application, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of the stated features. In the description of this application, "a plurality of" means two or more, unless otherwise explicitly specified.

[0040] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0041] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0042] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0043] Please seeFigure 1 and Figure 9 The application provides a protective screen device 100, which is connected to an air inlet 201 of a molecular pump when the molecular pump is started, and is used for filtering impurities in air when the molecular pump is exhausted.

[0044] Please refer to Figure 2 and Figure 3 The protective screen device 100 provided by the application comprises a mounting cylinder 30, a first sieve plate 10 and a second sieve plate 20. The mounting cylinder 30 has a first end 31 and a second end 32 opposite to each other. The first sieve plate 10 is fixedly arranged at the first end 31, and a plurality of first through holes 11 are distributed on the first sieve plate 10. The second sieve plate 20 is arranged on a side of the first sieve plate 10 close to the second end 32 and is movably arranged in the mounting cylinder 30 along the central axis direction of the mounting cylinder 30 so as to be attached to or separated from the first sieve plate 10. A plurality of second through holes 21 corresponding to the first through holes 11 are distributed on the second sieve plate 20, the aperture of the second through holes 21 is smaller than that of the first through holes 11, and the gaps between the plurality of second through holes 21 are distributed with a plurality of third through holes 22, the aperture of the third through holes 22 is larger than that of the second through holes 21, and the gaps between the plurality of third through holes 22 correspond to the gaps between the plurality of first through holes 11. In this way, when the second sieve plate 20 is moved to be attached to the first sieve plate 10, the gas passes through the second sieve plate 20 through the second through holes 21; when the second sieve plate 20 is moved to be separated from the first sieve plate 10, the gas passes through the second sieve plate 20 through the second through holes 21 and the third through holes 22.

[0045] By arranging the movable second sieve plate 20 on one side of the first sieve plate 10 in the mounting cylinder 30 of the protective screen device 100, the aperture through which the gas passes through the second sieve plate 20 can be adjusted by moving the second sieve plate 20 to be attached to or separated from the first sieve plate 10. In the initial stage of starting the molecular pump, the gas flow is large, so the second sieve plate 20 can be moved to be separated from the first sieve plate 10, at this time, the gas at the first end 31 of the mounting cylinder 30 first passes through the first through holes 11 of the first sieve plate 10, and then passes through the second through holes 21 and the third through holes 22 of the second sieve plate 20 to enter the air inlet 201 of the molecular pump, so that the impact of the large gas flow on the protective screen device 100 can be avoided; as the molecular pump operates, the gas flow decreases and the gas flow impact force weakens, so the second sieve plate 20 can be moved to be attached to the first sieve plate 10, at this time, the third through holes 22 of the second sieve plate 20 are closed by the first sieve plate 10, and the gas at the first end 31 of the mounting cylinder 30 only blows to the air inlet 201 of the molecular pump through the second through holes 21. Since according to the working principle of the vacuum equipment such as the molecular pump, in the vacuum pumping process, almost more than 99% of the time is in a state of small gas flow, the protective screen device 100 provided by the application can effectively increase the filtration of large-particle impurities in air, reduce the entry of large particles into the molecular pump, protect the stable operation of the molecular pump, and improve the service life of the molecular pump.

[0046] The installation cylinder 30 in the protective screen device 100 is a cylindrical structure, the first end 31 of the installation cylinder 30 is provided with the first sieve plate 10 for gas to enter, and the second end 32 of the installation cylinder 30 is connected with the molecular pump to enable the gas to enter the molecular pump. It can be understood that the installation cylinder 30 is a cylindrical structure with both ends open. The cross-sectional shape of the installation cylinder 30 can correspond to the shape of one end of the molecular pump gas inlet 201, for example, the installation cylinder 30 can be a cylindrical structure, but is not limited thereto. The second end 32 of the installation cylinder 30 can be provided with a connecting flange 33, and the protective screen device 100 is connected with the molecular pump by providing connecting bolts on the connecting flange 33.

[0047] The first sieve plate 10 is fixedly arranged at the first end 31 of the installation cylinder 30, and can be welded, clamped, riveted or connected by a threaded fastener, but is not limited thereto. The first sieve plate 10 is distributed with a plurality of first through holes 11, which can be uniformly distributed on the first sieve plate 10.

[0048] The second through hole 21 on the second sieve plate 20 corresponds to the first through hole 11, which means that the number of the second through hole 21 is the same as that of the first through hole 11, and the center axes of the corresponding second through hole 21 and the first through hole 11 are on the same straight line. In this way, after the second sieve plate 20 is attached to the first sieve plate 10, the actual aperture for the gas to pass through at the first through hole 11 and the second through hole 21 is equivalent to the aperture of the second through hole 21. Since the third through hole 22 is distributed in the gap between the second through hole 21, and the gap between the third through hole 22 and the first through hole 11 corresponds, wherein the gap between the third through hole 22 and the first through hole 11 corresponds means that in the direction along the center axes of the first through hole 11 and the third through hole 22, the third through hole 22 is distributed in the gap region of the first through hole 11, that is, the third through hole 22 is projected along the center axis direction of the first sieve plate, and the projection of the third through hole 22 falls in the gap region of the first through hole 11. In this way, after the second sieve plate 20 is attached to the first sieve plate 10, the gap of the first sieve plate 10 can cover the third through hole 22, which is equivalent to that only the second through hole 21 of the first sieve plate 10 and the second sieve plate 20 provides the gas through hole.

[0049] Please refer to Figures 4 to 8 , wherein Figure 7 and Figure 8 The arrow direction of the straight line in Figure 4 and Figure 6As shown, the second screen plate 20 has a plurality of protrusions 23 on the side facing the first screen plate 10, and the second through holes 21 are formed on the protrusions 23. When the second screen plate 20 is moved to be attached to the first screen plate 10, the protrusions 23 are inserted into the first through holes 11; when the second screen plate 20 is moved to be separated from the first screen plate 10, the protrusions 23 are separated from the first through holes 11. The height of the protrusions 23 protruding from the second screen plate 20 can be not less than the thickness of the first screen plate 10, so that the upper end surface of the protrusions 23 is flush with or protrudes from the first screen plate 10 after the second screen plate 20 is attached to the first screen plate 10, preventing impurities from being stuck in the first through holes 11 and reducing the frequency of cleaning the protective screen device 100 during use.

[0050] As shown in Figure 4 and Figure 8 In some embodiments, the first through holes 11 can be tapered holes, and the corresponding protrusions 23 on the second screen plate 20 can also be tapered protrusions 23. The tapered holes and the tapered protrusions 23 have small-diameter ends near the first end 31 of the mounting cylinder 30, which ensures that the protrusions 23 can be accurately inserted into the first through holes 11 when the second screen plate 20 is moved to the first screen plate 10.

[0051] The second screen plate 20 is movably arranged in the mounting cylinder 30 along the central axis of the mounting cylinder 30 to adjust the pore size for gas passing through by moving to be attached to the first screen plate 10 or moving to be separated from the first screen plate 10. The second screen plate 20 can be movably arranged in the mounting cylinder 30 by an elastic member 60 or by a linear motion driving mechanism, which can be a lead screw and sliding block mechanism, a gear and rack mechanism, or a pneumatic cylinder assembly, but is not limited thereto. It should be noted that when the second screen plate 20 is movably arranged in the mounting cylinder 30 by the elastic member 60, the second screen plate 20 can be moved to be close to or away from the first screen plate 10 under the action of the gas flow pressure and the pressure of the elastic member 60; when the second screen plate 20 is movably arranged in the mounting cylinder 30 by the linear motion driving mechanism, the second screen plate 20 can be moved to be close to or away from the first screen plate 10 by manually controlling the linear motion driving mechanism to drive the second screen plate 20.

[0052] As shown in Figure 2 and Figure 4As shown, in some embodiments, the second sieve plate 20 is movably disposed within the mounting cylinder 30 via an elastic member 60. The elastic member 60 is configured such that when the gas pressure on the side of the second sieve plate 20 closest to the first sieve plate 10 is greater than a specified value, the second sieve plate 20 can squeeze the elastic member 60 to separate from the first sieve plate 10; when the gas pressure on the side of the second sieve plate 20 closest to the first sieve plate 10 is less than a specified value, the elastic member 60 can press the second sieve plate 20 into contact with the first sieve plate 10. The elastic member 60 can be a spring, but is not limited to this. The specified value can be determined based on the wind pressure experienced by the second sieve plate 20 when the molecular pump is first started. Thus, when the gas flow rate is large, the second sieve plate 20 can squeeze the elastic member 60 to separate from the first sieve plate 10 under the action of the airflow; as the airflow rate decreases, the second sieve plate 20 can be pressed against the first sieve plate 10 by the squeezing action of the elastic member 60, allowing the protective net device 100 to automatically adjust the aperture of the second sieve plate 20 for gas passage according to the gas flow rate.

[0053] like Figure 2 , Figures 4 to 6 As shown, in some embodiments, the protective net device 100 may further include a fixing plate 40, which is fixedly disposed within the mounting cylinder 30 and located on the side of the second screen plate 20 away from the first screen plate 10. Simultaneously, a connecting rod 25 is provided on the side of the second screen plate 20 closest to the fixing plate 40. One end of an elastic member 60 is connected to the connecting rod 25, and the other end is connected to the fixing plate 40. For example, when the elastic member 60 is a spring, it can be sleeved on the connecting rod 25, but is not limited thereto. For example, in some embodiments, the connecting rod 25 may pass through the fixing plate 40, and a first limiting structure 251 and a second limiting structure 252 are provided on the connecting rod 25. The first limiting structure 251 is located on the side of the fixing plate 40 closest to the second screen plate 20, and the second limiting structure 252 is located on the side of the fixing plate 40 away from the second screen plate 20. Thus, the first limiting structure 251 and the second limiting structure 252 can limit the vertical movement range of the second screen plate 20. Taking the example of the elastic element 60 being fitted onto the connecting rod 25, one end of the elastic element 60 connected to the connecting rod 25 can be connected to the first limiting structure 251. The first limiting structure 251 can be a shoulder structure formed on the connecting rod 25, or a limiting block fixedly mounted on the connecting rod 25. Correspondingly, to facilitate the disassembly of the connecting rod 25, the second limiting structure 252 can be a limiting block, which can be detachably mounted on the connecting rod 25. For example, it can be a snap-fit, threaded connection, or threaded fastener connection, but it is not limited to these.

[0054] It should be noted that, in order to enable the gas passing through the second sieve plate 20 to enter the gas inlet 201 of the molecular pump, in some embodiments, the fourth through hole 41 is further arranged on the fixed plate 40. The aperture of the fourth through hole 41 can be smaller than the aperture of the second through hole 21, further filtering impurities and ensuring the normal operation of the molecular pump.

[0055] As shown in Figure 2 , Figure 4 and Figure 5 , in some embodiments, the protective net device 100 further comprises a guide column 50. The guide column 50 is arranged along the moving direction of the second sieve plate 20. Correspondingly, the second sieve plate 20 is provided with a guide groove 24 matched with the guide column 50. Thus, the second sieve plate 20 can be prevented from rotating during the up-down movement, and the central axes of the second through hole 21 and the first through hole 11 can be kept on the same straight line.

[0056] In some embodiments, the guide column 50 is fixedly arranged on the inner wall of the mounting cylinder 30, and one end of the guide column 50 abuts against the side of the first sieve plate 10 close to the second sieve plate 20. By fixing the guide column 50 on the inner wall of the mounting cylinder 30, and correspondingly, distributing the guide grooves 24 on the edge of the second sieve plate 20, the guide grooves 24 can be prevented from affecting the distribution of the second through hole 21 and the third through hole 22 on the second sieve plate 20. It can be understood that the shape of the guide groove 24 corresponds to the cross-sectional shape of the guide column 50, and the cross-sectional shape of the guide column 50 is not limited in the embodiments of the present application, for example, it can be rectangular, triangular or arc-shaped. By abutting the one end of the guide column 50 against the first sieve plate 10, on the one hand, the guide column 50 can support the first sieve plate 10 to a certain extent, and on the other hand, the end of the guide column 50 can also position the installation of the first sieve plate 10. In some embodiments, in order to ensure the stability of the movement of the second sieve plate 20, two guide columns 50 can be arranged, and the two guide columns 50 are oppositely arranged along the radial direction of the mounting cylinder 30 in the mounting cylinder 30.

[0057] In other embodiments, the present application further provides a molecular pump, which comprises a pump body 200 and the protective net device 100 in any of the above embodiments. The pump body 200 has a gas inlet 201 and an exhaust port 202, and the protective net device 100 is arranged in the pump body 200, and the second end 32 of the mounting cylinder 30 in the protective net device 100 is connected with the gas inlet 201 of the pump body 200.

[0058] As shown in Figure 9 , when the molecular pump provided by the present application is used for vacuumizing the cavity 300, the protective net device 100 of the molecular pump is arranged in the cavity 300, and the pump body 200 is arranged outside the cavity 300.

[0059] The molecular pump provided in the application adopts all the technical solutions of all the embodiments of the protective net device 100, and thus has all the beneficial effects brought by the technical solutions of the embodiments of the protective net device 100, which will not be repeated here.

[0060] The above is only an embodiment of the application, and does not limit the patent scope of the application. Any equivalent structure or equivalent process transformation using the content of the specification and drawings, or direct or indirect application in other related technical fields, is also included in the patent protection scope of the application.

Claims

1. A protective net device for a molecular pump, characterized in that, The protective netting device includes: The mounting cylinder has a first end and a second end opposite to each other, the second end being used for connection to a molecular pump; A first sieve plate is fixedly disposed at the first end, and a plurality of first through holes are distributed on the first sieve plate; The second sieve plate is located on the side of the first sieve plate near the second end, and is movably disposed in the mounting cylinder along the central axis of the mounting cylinder to fit or separate from the first sieve plate; the second sieve plate has a plurality of second through holes corresponding to the first through holes, the diameter of the second through holes being smaller than the diameter of the first through holes, and a plurality of third through holes are distributed between the plurality of second through holes, the diameter of the third through holes being larger than the diameter of the second through holes, and the gaps between the plurality of third through holes correspond to the gaps between the plurality of first through holes.

2. The protective netting device as described in claim 1, characterized in that, The second sieve plate has a plurality of protrusions on the side facing the first sieve plate that cooperate with the first through hole. The second through hole is formed on the protrusion. When the second sieve plate moves to fit against the first sieve plate, the protrusion is embedded in the first through hole. When the second sieve plate moves to separate from the first sieve plate, the protrusion is dislodged from the first through hole.

3. The protective netting device as described in claim 2, characterized in that, The first through hole is a tapered hole, and the protrusion is a tapered protrusion. The ends of the tapered hole and the tapered protrusion closest to the first end are both small-diameter ends.

4. The protective netting device as described in claim 1, characterized in that, The second sieve plate is movably disposed in the mounting cylinder by means of an elastic element. The elastic element is configured such that when the gas pressure on the side of the second sieve plate close to the first sieve plate is greater than a specified value, the second sieve plate can squeeze the elastic element to separate from the first sieve plate. When the gas pressure on the side of the second sieve plate closer to the first sieve plate is less than a specified value, the elastic element can squeeze the second sieve plate to fit against the first sieve plate.

5. The protective netting device as described in claim 4, characterized in that, The protective netting device also includes: A fixing plate is fixedly installed inside the mounting cylinder and located on the side of the second sieve plate away from the first sieve plate; A connecting rod is provided on the side of the second sieve plate near the fixed plate. One end of the elastic element is connected to the connecting rod, and the other end is connected to the fixed plate.

6. The protective netting device as described in claim 5, characterized in that, The connecting rod passes through the fixed plate and is provided with a first limiting structure and a second limiting structure. The first limiting structure is located on the side of the fixed plate closer to the second sieve plate, and the second limiting structure is located on the side of the fixed plate away from the second sieve plate.

7. The protective netting device as described in claim 5, characterized in that, The fixing plate has a plurality of fourth through holes, the diameter of which is smaller than that of the second through holes.

8. The protective netting device as described in claim 1, characterized in that, The protective netting device also includes: Guide columns are provided along the moving direction of the second sieve plate; The second sieve plate is provided with a guide groove that cooperates with the guide post.

9. The protective netting device as described in claim 8, characterized in that, The guide post is fixedly installed on the inner wall of the mounting cylinder, and one end of the guide post abuts against the side of the first sieve plate near the second sieve plate.

10. A molecular pump, characterized in that, The molecular pump includes: The pump body has an air inlet and an exhaust outlet; The protective net device according to any one of claims 1-9, wherein the protective net device is disposed in the pump body, and the second end is connected to the air inlet.

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