Device for detecting assembly quality of vacuum molecular pump blade

Abstract

The invention relates to the technical field of vacuum molecular pump blade assembly quality detection, which comprises a detection table, a protective shell is arranged at the top end of the detection table, an opening and closing assembly is arranged on one side of the protective shell, a rotating table is arranged at the top end of the detection table and located in the protective shell, and an impeller is arranged at the top end of the rotating table. A limiting mechanism matched with the impeller is arranged at the top end of the rotating table, laser displacement sensors are symmetrically arranged at the top end of the impeller, and the two sets of laser displacement sensors are connected with the protective shell through a movable adjusting assembly. The device has the beneficial effects that rotation detection can be conducted on the impeller by arranging the rotating table, the driving motor and the laser displacement sensor, the laser displacement sensor can detect whether blades of the impeller move or not in the rotating process, then whether the blades are firmly installed or not is judged, manual detection is not needed, and safety and efficiency are higher; by arranging the protective shell and the opening and closing assembly, the impeller can be completely sealed and covered in the detection process, and blades are prevented from flying out to injure people accidentally.

Description

Technical Field

[0001] This invention relates to the field of vacuum molecular pump blade assembly quality testing technology, and more specifically, to a device for testing the assembly quality of vacuum molecular pump blades. Background Technology

[0002] A molecular pump is a vacuum device that uses a high-speed rotating rotor to transfer momentum to compress and expel gases. It is classified into three types: traction type, turbine type, and combined type, with an operating pressure range covering 10⁻⁻⁴. 6 ~1Pa. The turbomolecular pump employs a rotor speed of up to 20,000 rpm and can produce pressures below 10⁻¹. 0 Vacuum levels of Pa are used in high-precision fields such as semiconductor manufacturing and electron microscopy. Composite molecular pumps combine the pumping speed of a turbine stage with the compression ratio of a traction stage, employing helical groove or cylindrical groove structures to reduce gas backflow. They require a backing pump to achieve optimal performance.

[0003] After the vacuum molecular pump blades are assembled, they need to be inspected to ensure that the assembled blades are secure and compliant. Currently, most inspections rely on manual quality checks of the blades. Since there are many blades after the blades are assembled into an impeller, and the blades are relatively separate, it is easy for personnel to accidentally injure themselves during manual inspection, and the inspection efficiency is low.

[0004] No effective solutions have yet been proposed to address the problems in the relevant technologies. Summary of the Invention

[0005] To address the problems in related technologies, this invention proposes a device for detecting the assembly quality of vacuum molecular pump blades, thereby overcoming the aforementioned technical problems existing in the prior art.

[0006] Therefore, the specific technical solution adopted by the present invention is as follows: A device for detecting the assembly quality of vacuum molecular pump blades includes a testing platform. A protective shell is located at the top of the testing platform, and an opening / closing assembly is located on one side of the protective shell. A rotating platform is located at the top of the testing platform and within the protective shell. An impeller is located at the top of the rotating platform, and a limiting mechanism matching the impeller is located at the top of the rotating platform. Symmetrically arranged laser displacement sensors are located at the top of the impeller. Two sets of laser displacement sensors are connected to the protective shell via a moving adjustment assembly. The moving adjustment assembly includes an adjustment box located at the top of the protective shell. A horizontally arranged bidirectional lead screw is located within the adjustment box. Symmetrically arranged L-shaped connecting frames extending outside the adjustment box and connected to the laser displacement sensors are fitted onto the outer wall of the bidirectional lead screw. A helical gear is fixedly fitted between the two sets of L-shaped connecting frames and onto the outer wall of the bidirectional lead screw. A matching helical gear is located at the bottom of the helical gear. The helical gear is connected to the adjustment box via a connecting shaft, the bottom of which extends outside the adjustment box and connects to a knob.

[0007] Preferably, the bidirectional lead screw is connected to the adjusting box via a bearing, and both sets of L-shaped connecting frames are provided with threaded holes that match the bidirectional lead screw.

[0008] Preferably, the testing platform has a placement slot, a drive motor is provided in the placement slot, the drive end of the drive motor extends to the outside of the testing platform and connects to the rotating platform, a support sleeve is fitted on the top of the testing platform and on the outer wall of the rotating platform, a support groove is provided on the inner wall of the support sleeve, and a support ring matching the support groove is fixedly fitted on the outer wall of the rotating platform, with a number of evenly distributed rolling balls at both ends of the support ring.

[0009] Preferably, the testing platform has heat dissipation holes on one side that match the placement slot.

[0010] Preferably, the opening and closing assembly includes a movable cover plate at the top of the protective shell, a sliding groove matching the movable cover plate on the inner wall of the protective shell, an observation window on the movable cover plate, and a drive assembly matching the movable cover plate on the protective shell.

[0011] Preferably, the drive assembly includes symmetrically arranged mounting holes at the top of the protective shell, a drive shaft passing through the two sets of mounting holes in the protective shell, a gear fixedly sleeved in the mounting hole and on the outer wall of the drive shaft, a rack provided on one side of the movable cover plate and matched with the gear, and one end of the drive shaft extending outside the protective shell and connected to a drive end of a servo motor.

[0012] Preferably, the limiting mechanism includes a positioning column at the top of the rotating platform, a plurality of extrusion columns arranged in a circular array within the positioning column, a bidirectional lead screw II between the plurality of extrusion columns arranged in a circular array, symmetrically arranged moving blocks sleeved on the outer wall of the bidirectional lead screw II, both sets of moving blocks being connected to the extrusion columns via extrusion rods, a limiting key on one side of the extrusion column, a keyway matching the limiting key on the inner wall of the impeller, and the extrusion column having an arc surface on the side of the limiting key.

[0013] Preferably, the second bidirectional lead screw is connected to the positioning post via the second bearing, and the top end of the second bidirectional lead screw extends to the outside of the positioning post and is connected to the second knob. Both sets of moving blocks are provided with threaded holes that match the second bidirectional lead screw. The positioning post is provided with guide rods that are symmetrically arranged and pass through the two sets of moving blocks. The moving blocks are provided with sliding holes that match the guide rods.

[0014] Preferably, the two ends of the extrusion rod are hinged to the extrusion column and the moving block respectively, and the outer wall of the positioning column is provided with an inlet and outlet that matches the extrusion column.

[0015] Preferably, the top of the rotating platform has symmetrically arranged stroke grooves, and a lead screw is provided in the stroke groove. The outer wall of the lead screw is provided with an L-shaped pressure frame extending out of the stroke groove. The lead screw is connected to the rotating platform through a bearing three. The L-shaped pressure frame is provided with a threaded hole three that matches the lead screw. One end of the lead screw extends out of the rotating platform and is connected to a knob three.

[0016] The beneficial effects of this invention are as follows: By setting a rotating platform, a drive motor, and a laser displacement sensor, the impeller rotation can be detected. The laser displacement sensor can detect whether the blades move during the rotation of the impeller, thereby determining whether the blades are securely installed. This eliminates the need for manual inspection, making it safer and more efficient. By setting a protective shell and an opening and closing assembly, the impeller can be completely covered during the detection process, preventing blades from flying out and injuring personnel. By setting a limiting mechanism, the impeller can be fixed on the rotating platform. At the same time, the limiting mechanism, through the cooperation of positioning columns, bidirectional lead screws, moving blocks, extrusion columns, extrusion rods, and limiting keys, ensures that multiple sets of extrusion columns can fully extrude and contact the inner wall of the impeller, preventing the impeller from becoming loose and affecting the detection accuracy. By setting a moving adjustment assembly, the position of the laser displacement sensor can be adjusted, making it more flexible and convenient to use. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the overall structure of a device for detecting the assembly quality of vacuum molecular pump blades according to an embodiment of the present invention. Figure 2 This is a schematic diagram of a vacuum molecular pump blade assembly quality detection device from another angle according to an embodiment of the present invention. Figure 3 This is a front view of a device for detecting the assembly quality of vacuum molecular pump blades according to an embodiment of the present invention. Figure 4 yes Figure 2 A magnified view of a portion of point A in the middle; Figure 5 This is a cross-sectional view of a device for detecting the assembly quality of vacuum molecular pump blades according to an embodiment of the present invention. Figure 6 yes Figure 5 A magnified view of a portion of point B in the middle; Figure 7 This is a diagram showing the impeller placement of a device for detecting the assembly quality of vacuum molecular pump blades according to an embodiment of the present invention. Figure 8 This is a schematic diagram of the rotating stage in a device for detecting the assembly quality of vacuum molecular pump blades according to an embodiment of the present invention. Figure 9 This is a schematic diagram of the internal structure of the positioning column in a vacuum molecular pump blade assembly quality detection device according to an embodiment of the present invention.

[0019] In the picture: 1. Testing table; 2. Protective shell; 3. Rotating table; 4. Impeller; 5. Laser displacement sensor; 6. Bidirectional lead screw I; 7. L-shaped connecting frame; 8. Adjustment box; 9. Helical gear I; 10. Helical gear II; 11. Connecting shaft; 12. Knob I; 13. Drive motor; 14. Support sleeve; 15. Support groove; 16. Support ring; 17. Ball bearing; 18. Heat dissipation hole; 19. Movable cover plate; 20. Slide groove; 21. Observation window; 22. Mounting hole; 23. Drive shaft; 24. Gear; 25. Rack; 26. Servo motor I; 27. Positioning column; 28. Extrusion column; 29. ​​Bidirectional lead screw II; 30. Moving block; 31. Limit key; 32. Knob II; 33. Guide rod; 34. Stroke groove; 35. Lead screw; 36. L-shaped pressure frame; 37. Knob III; 38. Placement groove; 39. Extrusion rod. Detailed Implementation

[0020] To further illustrate the various embodiments, the present invention provides accompanying drawings, which are part of the disclosure of the present invention. These drawings are mainly used to illustrate the embodiments and can be used in conjunction with the relevant descriptions in the specification to explain the operating principles of the embodiments. With reference to these drawings, those skilled in the art should be able to understand other possible implementation methods and the advantages of the present invention. The components in the drawings are not drawn to scale, and similar component symbols are generally used to represent similar components.

[0021] According to an embodiment of the present invention, a device for detecting the assembly quality of vacuum molecular pump blades is provided. Example

[0022] like Figure 1-9 As shown, the vacuum molecular pump blade assembly quality detection device according to an embodiment of the present invention includes a detection platform 1, a protective shell 2 at the top of the detection platform 1, an opening and closing assembly on one side of the protective shell 2, a rotating platform 3 at the top of the detection platform 1 and located within the protective shell 2, an impeller 4 at the top of the rotating platform 3, a limiting mechanism matching the impeller 4 at the top of the rotating platform 3, and symmetrically arranged laser displacement sensors 5 at the top of the impeller 4. Two sets of laser displacement sensors 5 are connected to the protective shell 2 via a movement adjustment assembly, the movement adjustment assembly including the protective shell. An adjustment box 8 is located at the top of the inner part of the unit 2. The adjustment box 8 contains a horizontally arranged bidirectional lead screw 6. The outer wall of the bidirectional lead screw 6 is fitted with symmetrically arranged L-shaped connecting brackets 7 that extend outside the adjustment box 8 and connect to the laser displacement sensor 5. A helical gear 9 is fixedly fitted between the two sets of L-shaped connecting brackets 7 and on the outer wall of the bidirectional lead screw 6. The bottom end of the helical gear 9 has a matching helical gear 10. The helical gear 10 is connected to the adjustment box 8 via a connecting shaft 11. The bottom end of the connecting shaft 11 extends outside the adjustment box 8 and connects to a knob 12. The bidirectional lead screw 6 is connected to the adjustment box 8 via a bearing. Both sets of L-shaped connecting brackets 7 have threaded holes matching the bidirectional lead screw 6. The testing platform 1 has a placement slot 38, and a drive motor 13 is installed in the placement slot 38. The drive end of the drive motor 13 extends to the outside of the testing platform 1 and connects to the rotating platform 3. A support sleeve 14 is fitted on the top of the testing platform 1 and on the outer wall of the rotating platform 3. A support groove 15 is formed on the inner wall of the support sleeve 14. A support ring 16 matching the support groove 15 is fixedly fitted on the outer wall of the rotating platform 3. Both ends of the support ring 16 are provided with a plurality of evenly distributed rolling balls 17. A heat dissipation hole 18 matching the placement slot 38 is formed on one side of the testing platform 1.

[0023] During testing, after assembling the blades into impeller 4, impeller 4 is placed on the rotating table 3 and fixed by the limiting mechanism. Then, the operator rotates knob 12, which drives the connecting shaft 11 to rotate. The connecting shaft 11 drives helical gear 10 to rotate, which in turn drives helical gear 9 to rotate. Helical gear 9 drives the bidirectional lead screw 6 to rotate, which in turn drives the two sets of L-shaped connecting frames 7 to move closer or further apart. The two sets of L-shaped connecting frames 7 respectively drive the two sets of laser displacement sensors to move closer or further apart. After the laser displacement sensors are moved to the appropriate position, the opening and closing assembly is activated to completely cover the protective shell 2. Then, the drive motor 13 is started to rotate the rotating table 3. The impeller 4 is driven to rotate at high speed. The rotating platform 3 is connected to the support sleeve 14 through the support ring 16 and the ball 17, so that the rotating platform 3 rotates stably. When the impeller 4 rotates at high speed, if the blades become loose, the laser displacement sensor will send the monitored information to the external display device for viewing. By setting the rotating platform, drive motor and laser displacement sensor, the rotation of the impeller can be detected. The laser displacement sensor can detect whether the blades of the impeller move during the rotation, and thus determine whether the blades are installed firmly. It is safer and more efficient without manual inspection. The position of the laser displacement sensor can be adjusted by setting the movement adjustment component, making it more flexible and convenient to use. Example

[0024] like Figure 1-9 As shown, the opening and closing assembly includes a movable cover plate 19 at the top of the protective shell 2, a sliding groove 20 matching the movable cover plate 19 on the inner wall of the protective shell 2, an observation window 21 on the movable cover plate 19, and a drive assembly matching the movable cover plate 19 on the protective shell 2. The drive assembly includes symmetrically arranged mounting holes 22 at the top of the protective shell 2, a drive shaft 23 penetrating through the two sets of mounting holes 22 in the protective shell 2, a gear 24 fixedly sleeved in the mounting holes 22 and located on the outer wall of the drive shaft 23, a rack 25 matching the gear 24 on one side of the movable cover plate 19, and one end of the drive shaft 23 extending outside the protective shell 2 and connected to the drive end of a servo motor 26.

[0025] When using the opening and closing assembly, the servo motor 26 is started to drive the drive shaft 23 to rotate. The drive shaft 23 drives the gear 24 to rotate. Since the gear 24 meshes with the rack 25, when the gear 24 rotates, it will drive the movable cover plate 19 to move downward through the rack 25 to cover the protective shell 2. Personnel can observe the impeller rotation through the observation window 21 on the movable cover plate 19. By setting the protective shell and the opening and closing assembly, the impeller can be completely covered during the detection process to prevent the blades from flying out and accidentally injuring personnel. Example

[0026] like Figure 1-9As shown, the limiting mechanism includes a positioning post 27 at the top of the rotating platform 3. The positioning post 27 has several extrusion posts 28 arranged in a circular array. A bidirectional lead screw 29 is provided between the extrusion posts 28 arranged in a circular array. The outer wall of the bidirectional lead screw 29 is fitted with symmetrically arranged moving blocks 30. Both sets of moving blocks 30 are connected to the extrusion posts 28 through extrusion rods 39. A limiting key 31 is provided on one side of the extrusion post 28. A keyway matching the limiting key 31 is opened on the inner wall of the impeller 4. The side of the extrusion post 28 located on the limiting key 31 is an arc surface. The second bidirectional lead screw 29 is connected to the positioning post 27 via a bearing 2. The top end of the second bidirectional lead screw 29 extends outside the positioning post 27 and connects to the second knob 32. Both sets of moving blocks 30 have threaded holes 2 that match the second bidirectional lead screw 29. The positioning post 27 has guide rods 33 symmetrically arranged and penetrating both sets of moving blocks 30. The moving blocks 30 have sliding holes that match the guide rods 33. The two ends of the extrusion rod 39 are hinged to the extrusion post 28 and the moving blocks 30, respectively. The outer wall of the positioning post 27 has an inlet and outlet that match the extrusion post 28. The top of the rotating platform 3 is provided with symmetrically arranged stroke grooves 34. A lead screw 35 is provided in the stroke groove 34. An L-shaped pressure frame 36 extending out of the stroke groove 34 is provided on the outer wall of the lead screw 35. The lead screw 35 is connected to the rotating platform 3 through a bearing 3. A threaded hole 3 matching the lead screw 35 is provided on the L-shaped pressure frame 36. One end of the lead screw 35 extends out of the rotating platform 3 and is connected to a knob 37.

[0027] When fixing the impeller 4, place the impeller 4 on the rotating platform 3, so that the positioning post 27 on the rotating platform 3 passes through the mounting hole on the impeller 4, and the limit key 31 enters the keyway on the inner wall of the impeller 4. Then, the operator rotates the knob 32 to drive the double-acting screw 29 to rotate. The double-acting screw 29 drives the two sets of moving blocks 30 to move close together. The two sets of moving blocks 30 drive multiple sets of extrusion posts 28 to expand outward from the positioning post 27 through the extrusion rod 39, so that the arc surface of the positioning post 27 is tightly extruded with the inner wall of the impeller 4. To prevent the impeller from loosening, the operator rotates knob 37 to rotate screw 35. Screw 35 then moves L-shaped pressure frame 36 closer to the impeller 4 until L-shaped pressure frame 36 presses the disc on the impeller 4 tightly. By setting a limiting mechanism, the impeller can be fixed on the rotating table. At the same time, the limiting mechanism, through the cooperation of positioning column, bidirectional screw 2, moving block, extrusion column, extrusion rod and limiting key, ensures that multiple sets of extrusion columns can fully extrude and contact the inner wall of the impeller, avoiding the impeller from loosening and affecting the detection accuracy.

[0028] In summary, by utilizing the above-mentioned technical solution of the present invention, the impeller rotation can be detected by setting up a rotating platform, a drive motor, and a laser displacement sensor. The laser displacement sensor can detect whether the blades of the impeller move during rotation, thereby determining whether the blades are securely installed. This eliminates the need for manual inspection, making it safer and more efficient. By setting up a protective shell and an opening and closing assembly, the impeller can be completely covered during the detection process, preventing blades from flying out and injuring personnel. By setting up a limiting mechanism, the impeller can be fixed on the rotating platform. At the same time, the limiting mechanism, through the cooperation of positioning columns, bidirectional lead screws, moving blocks, extrusion columns, extrusion rods, and limiting keys, ensures that multiple sets of extrusion columns can fully compress and contact the inner wall of the impeller, preventing the impeller from becoming loose and affecting the detection accuracy. By setting up a moving adjustment assembly, the position of the laser displacement sensor can be adjusted, making it more flexible and convenient to use.

[0029] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A device for detecting the assembly quality of vacuum molecular pump blades, characterized in that, The system includes a testing platform (1), a protective shell (2) at the top of the testing platform (1), an opening and closing assembly on one side of the protective shell (2), a rotating platform (3) at the top of the testing platform (1) and inside the protective shell (2), an impeller (4) at the top of the rotating platform (3), a limiting mechanism matching the impeller (4) at the top of the rotating platform (3), and symmetrically arranged laser displacement sensors (5) at the top of the impeller (4). Two sets of laser displacement sensors (5) are connected to the protective shell (2) via a moving adjustment assembly, which includes an adjustment box (8) at the top of the protective shell (2). The adjustment box (8) is provided with a horizontally arranged bidirectional lead screw (6). The outer wall of the bidirectional lead screw (6) is fitted with symmetrically arranged L-shaped connecting brackets (7) that extend to the outside of the adjustment box (8) and are connected to the laser displacement sensor (5). Between the two sets of L-shaped connecting brackets (7) and on the outer wall of the bidirectional lead screw (6), a helical gear (9) is fixedly fitted. The bottom end of the helical gear (9) is provided with a matching helical gear (10). The helical gear (10) is connected to the adjustment box (8) through a connecting shaft (11). The bottom end of the connecting shaft (11) extends to the outside of the adjustment box (8) and is connected to the knob (12).

2. The device for detecting the assembly quality of the vane of a vacuum molecular pump according to claim 1, characterized in that, The bidirectional lead screw (6) is connected to the adjustment box (8) through a bearing, and both sets of L-shaped connecting frames (7) are provided with threaded holes that match the bidirectional lead screw (6).

3. The device for detecting the quality of assembly of the vaned rotor of a vacuum molecular pump according to claim 1, characterized in that, The testing platform (1) has a placement slot (38) and a drive motor (13) in the placement slot (38). The drive end of the drive motor (13) extends to the outside of the testing platform (1) and is connected to the rotating platform (3). A support sleeve (14) is fitted on the top of the testing platform (1) and on the outer wall of the rotating platform (3). A support groove (15) is provided on the inner wall of the support sleeve (14). A support ring (16) matching the support groove (15) is fixedly fitted on the outer wall of the rotating platform (3). Several evenly distributed rolling balls (17) are provided at both ends of the support ring (16).

4. The device for detecting the quality of assembly of the vaned wheel of a vacuum molecular pump according to claim 3, characterized in that, The testing platform (1) has a heat dissipation hole (18) on one side that matches the placement slot (38).

5. The device for detecting the quality of assembly of the vaned rotor of a vacuum molecular pump according to claim 1, characterized in that, The opening and closing assembly includes a movable cover plate (19) provided at the top of the protective shell (2), a sliding groove (20) matching the movable cover plate (19) provided on the inner wall of the protective shell (2), an observation window (21) provided on the movable cover plate (19), and a driving assembly matching the movable cover plate (19) provided on the protective shell (2).

6. A device for detecting the quality of assembly of a blade of a vacuum molecular pump according to claim 5, characterized in that, The drive assembly includes symmetrically arranged mounting holes (22) at the top of the protective shell (2). The protective shell (2) has a drive shaft (23) that passes through the two sets of mounting holes (22). A gear (24) is fixedly sleeved in the mounting hole (22) and located on the outer wall of the drive shaft (23). A rack (25) is provided on one side of the movable cover plate (19) and matched with the gear (24). One end of the drive shaft (23) extends to the outside of the protective shell (2) and is connected to the drive end of a servo motor (26).

7. The device for detecting the quality of assembly of the vaned rotor of a vacuum molecular pump according to claim 1, characterized in that, The limiting mechanism includes a positioning column (27) at the top of the rotating table (3), a plurality of extrusion columns (28) arranged in a circular array in the positioning column (27), a bidirectional lead screw (29) between the plurality of extrusion columns (28) arranged in a circular array, and a symmetrically arranged moving block (30) sleeved on the outer wall of the bidirectional lead screw (29). Both sets of moving blocks (30) are connected to the extrusion column (28) through the extrusion rod (39). A limiting key (31) is provided on one side of the extrusion column (28), and a keyway matching the limiting key (31) is opened on the inner wall of the impeller (4). The extrusion column (28) is located on the side of the limiting key (31) with an arc surface.

8. The device for detecting the quality of assembly of the vaned wheel of a vacuum molecular pump according to claim 7, characterized in that, The second bidirectional lead screw (29) is connected to the positioning post (27) through the second bearing. The top end of the second bidirectional lead screw (29) extends to the outside of the positioning post (27) and is connected to the second knob (32). Both sets of moving blocks (30) are provided with threaded holes that match the second bidirectional lead screw (29). The positioning post (27) is provided with guide rods (33) that are symmetrically arranged and pass through the two sets of moving blocks (30). The moving blocks (30) are provided with sliding holes that match the guide rods (33).

9. The device for detecting the quality of assembly of the vaned wheel of a vacuum molecular pump according to claim 7, characterized in that, The two ends of the extrusion rod (39) are hinged to the extrusion column (28) and the moving block (30) respectively, and the outer wall of the positioning column (27) is provided with an inlet and outlet that matches the extrusion column (28).

10. The device for detecting the quality of assembly of the vaned wheel of a vacuum molecular pump according to claim 7, characterized in that, The top of the rotating platform (3) is provided with symmetrically arranged stroke grooves (34), and a lead screw (35) is provided in the stroke groove (34). The outer wall of the lead screw (35) is provided with an L-shaped pressure frame (36) extending to the outside of the stroke groove (34). The lead screw (35) is connected to the rotating platform (3) through a bearing three. The L-shaped pressure frame (36) is provided with a threaded hole three that matches the lead screw (35). One end of the lead screw (35) extends to the outside of the rotating platform (3) and is connected to a knob three (37).

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