A pitch carbon fiber raw yarn stranding device
By introducing stranding, winding, and cleaning components into the pitch carbon fiber stranding device, the problem of insufficient cleaning in traditional devices is solved, achieving efficient cleaning and winding processes, and improving product quality and device practicality.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- ZHENJIANG AOLITE MASCH MFG CO LTD
- Filing Date
- 2025-05-26
- Publication Date
- 2026-06-16
AI Technical Summary
Traditional pitch-carbon fiber stranding devices lack effective cleaning structures, resulting in impurities adhering to the surface of the stranded product, affecting its quality and aesthetics, and reducing its practicality.
An apparatus comprising a twisting component, a winding component, and a cleaning component is designed. The twisting component is used for twisting raw yarns, the winding component is used for winding, and the cleaning component is used for cleaning the surface of the twisted raw yarns by removing dust and other impurities with cleaning cotton.
It effectively improves the aesthetics and quality of pitch-carbon fiber, avoids damage to the product caused by impurities, and enhances the practicality of the equipment.
Smart Images

Figure CN224362289U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of pitch carbon fiber technology, specifically a pitch carbon fiber precursor stranding device. Background Technology
[0002] Pitch carbon fiber refers to a type of carbon fiber prepared from substances rich in polycyclic aromatic hydrocarbons, such as pitch, through polymerization, spinning, non-melting, and carbonization. In the production process of pitch carbon fiber, a pitch carbon fiber precursor stranding device is required.
[0003] Traditional twisting devices mostly lack an effective cleaning structure. After the raw yarn is twisted, a large amount of dust and other impurities may adhere to the surface of the twisted product. If the outer surface of the twisted product is not cleaned, the overall quality of the twisted product will be reduced, as will its overall aesthetics. Furthermore, some impurities may also affect the normal use of the twisted product, thus reducing the overall practicality of the twisting device.
[0004] Based on this, a device for stranding pitch-carbon fiber precursor fibers is now provided, which can eliminate the drawbacks of existing devices. Utility Model Content
[0005] The purpose of this invention is to provide a device for stranding pitch-carbon fiber precursor fibers to solve the problems in the prior art.
[0006] To achieve the above objectives, this utility model provides the following technical solution:
[0007] A device for stranding pitch carbon fiber precursor includes a base plate, a support plate fixedly connected to the right side of the upper surface of the base plate, a connecting plate provided on the left side of the support plate, the bottom of the connecting plate being fixedly connected to the upper surface of the base plate, a first motor being fixedly connected to the right side of the support plate, and a drive rod being fixedly connected to the output shaft of the first motor via a coupling, the other end of the drive rod being rotatably connected to the right side of the connecting plate.
[0008] The twisting assembly is located on the left side of the support plate and is used to twist the raw yarn.
[0009] The winding assembly is located on the upper left side of the base plate and at the discharge end of the twisting assembly. It is used to wind up the twisted raw yarn.
[0010] The cleaning component, located above the base plate and to the right of the winding component, is used to clean the surface of the twisted raw yarn.
[0011] Based on the above technical solutions, this utility model also provides the following optional technical solutions:
[0012] In one alternative embodiment: the plying assembly includes a turntable, a rotating rod fixedly connected to the center of the right side surface of the turntable, the other end of the rotating rod being rotatably connected to the left side surface of a support plate, a drive gear fixedly connected to the outside of a drive rod, a driven gear meshing with the drive gear fixedly connected to the outside of the rotating rod, multiple plying holes being formed through the left side surface of the turntable, a plying frame being fixedly mounted on the left side surface of the turntable, and multiple mounting frames being fixedly connected to the right side surface of the turntable, each mounting frame having an insert plate inside, and a raw yarn roller being fixedly connected to the right side surface of each insert plate.
[0013] In one alternative: multiple mounting frames are fixedly connected to the outside of a fixing block, the fixing block has a fixing rod inside, one end of the fixing rod extends to the outside of the fixing block and is fixedly connected to a pull plate, the fixing rod has a contact plate fixedly connected to the outside of the fixing rod, a return spring is sleeved on the outside of the fixing rod, the return spring abuts between the contact plate and the fixing block, the contact surfaces of the fixing block and the mounting frame are provided with guide grooves for the fixing rod to move, and the insert plate has a guide groove inside for the fixing rod to move.
[0014] In one alternative: the winding assembly includes a fixed frame fixedly connected to the left side of the upper surface of the base plate, a second motor fixedly connected to the front surface of the fixed frame, the output shaft of the second motor fixedly connected to a winding roller via a coupling, and the other end of the winding roller rotatably connected to the inner wall of the fixed frame.
[0015] In one alternative: mounting plates are symmetrically arranged in the middle of the upper surface of the base plate, and guide rollers are rotatably connected between the two mounting plates.
[0016] In one alternative: an adjusting plate is fixedly connected to the upper surface of the base plate, the adjusting plate is located to the left of the support plate, a third motor is fixedly connected to the front surface of the adjusting plate, the output shaft of the third motor is fixedly connected to a threaded rod through a coupling, the other end of the threaded rod is rotatably connected to the rear inner wall of the adjusting plate, a threaded block is threadedly connected to the external thread of the threaded rod, a guide groove for the threaded block to move is opened on the upper surface of the adjusting plate, and a traction frame is fixedly connected to the upper surface of the threaded block.
[0017] In one alternative embodiment: the cleaning assembly includes an L-shaped plate, the right side surface of which is fixedly connected to the left side surface of the threaded block; a guide groove for the L-shaped plate to move is provided on the left side surface of the adjusting plate; a lower plate is fixedly connected to the upper surface of the L-shaped plate; first side plates are fixedly connected to the front and rear surfaces of the lower plate; an upper plate is located directly above the lower plate; a handle is fixedly connected to the middle of the upper surface of the upper plate; second side plates are fixedly connected to the front and rear surfaces of the upper plate; a connecting rod is fixedly connected to the middle of the upper surface of each of the two first side plates; a limiting plate is fixedly connected to the other end of the connecting rod; a guide groove for the connecting rod to move is provided through the middle of the upper surface of each of the two second side plates; an abutting spring is sleeved on the outside of each of the two connecting rods; the two abutting springs abut against the limiting plate and the second side plates; and cleaning cotton is adhered to the opposite side of the upper and lower plates.
[0018] In one alternative: both connecting rods are fitted with accordion covers, and the two ends of the accordion covers are fixedly connected to the opposite side of the limiting plate and the second side plate, respectively.
[0019] Compared with the prior art, the beneficial effects of this utility model are as follows:
[0020] 1. This utility model, through the setting of the stranding component, can effectively strand the raw filament, thereby effectively producing and processing pitch carbon fiber.
[0021] 2. This utility model, through the setting of the winding component, can conveniently and effectively wind up the stranded raw yarn, thereby effectively collecting and processing the produced pitch carbon fiber.
[0022] 3. By incorporating a cleaning component, this invention can effectively clean the outer surface of the twisted pitch carbon fiber. This not only improves the overall aesthetics and quality of the pitch carbon fiber but also prevents impurities from damaging it, thus enhancing the overall practicality of the device. Attached Figure Description
[0023] Figure 1 This is a schematic diagram of the overall structure of this utility model.
[0024] Figure 2 This is a cross-sectional view of the fixing block in this utility model.
[0025] Figure 3 This is a cross-sectional structural diagram of the adjusting plate and the bellows cover in this utility model;
[0026] Figure 4 for Figure 2 Enlarged structural diagram of region A in the middle;
[0027] Figure 5 for Figure 3 A magnified structural diagram of region B in the middle;
[0028] Figure 6 This is a schematic diagram of the turntable and the stranding frame of this utility model.
[0029] Figure label annotations:
[0030] 1. Base plate; 2. Support plate; 3. First motor; 4. Turntable; 5. Mounting plate; 6. Guide roller; 7. Fixing frame; 8. Second motor; 9. Take-up roller; 10. Drive rod; 11. Connecting plate; 12. Drive gear; 13. Driven gear; 14. Rotating rod; 15. Twisting frame; 16. Adjusting plate; 17. Third motor; 18. Threaded rod; 19. Threaded block; 20. Traction frame; 21. L-shaped plate; 22. Mounting frame; 23. Insert plate; 24. Raw yarn roller; 25. Fixing block; 26. Fixing rod; 27. Contact plate; 28. Return spring; 29. Lower plate; 30. First side plate; 31. Upper plate; 32. Second side plate; 33. Connecting rod; 34. Limiting plate; 35. Contact spring; 36. Bellows protective cover; 37. Cleaning cotton; 38. Twisting hole. Detailed Implementation
[0031] To make the objectives, technical solutions, and advantages of this utility model clearer, the present utility model will be further described in detail below with reference to the accompanying drawings and embodiments.
[0032] In one embodiment, such as Figures 1-6 As shown, a device for stranding pitch carbon fiber precursor includes a base plate 1. A support plate 2 is fixedly connected to the right side of the upper surface of the base plate 1. A connecting plate 11 is provided on the left side of the support plate 2. The bottom of the connecting plate 11 is fixedly connected to the upper surface of the base plate 1. A first motor 3 is fixedly connected to the right side of the support plate 2. The output shaft of the first motor 3 is fixedly connected to a drive rod 10 through a coupling. The other end of the drive rod 10 is rotatably connected to the right side of the connecting plate 11.
[0033] A twisting assembly is located on the left side of the support plate 2 and is used to twist the raw yarn.
[0034] The winding assembly is located on the upper left side of the base plate 1 and at the discharge end of the twisting assembly, and is used to wind up the twisted raw yarn.
[0035] The cleaning component is located above the base plate 1 and to the right of the winding component, and is used to clean the surface of the twisted raw yarn.
[0036] In this embodiment, when it is necessary to perform stranding treatment on the precursor fibers of pitch carbon fiber, it is only necessary to first wrap one end of multiple precursor fibers around the outside of multiple precursor fiber rollers 24, then pass the other end of multiple precursor fibers through the inside of multiple stranding holes 38, and then pass the other end of multiple precursor fibers through the inside of the stranding frame 15 and wrap it around the outside of the winding assembly (when wrapping the precursor fibers around the outside of the winding assembly, the precursor fibers need to be passed through the inside of the cleaning assembly first). After the precursor fibers are wound, the stranding assembly starts to operate. At this time, the stranding assembly can effectively perform stranding treatment on multiple precursor fibers. During the operation of the stranding assembly, the winding assembly will also start to operate simultaneously. At this time, the winding assembly can effectively perform winding treatment on the stranded pitch carbon fiber. During the winding treatment of the stranded pitch carbon fiber, the cleaning assembly can effectively clean the dust and other impurities adhering to the surface of the pitch carbon fiber, thereby effectively improving the overall aesthetics and quality of the pitch carbon fiber after production and processing, and effectively improving the overall practicality of the device.
[0037] In one embodiment, such as Figures 1-3 As shown, the stranding assembly includes a turntable 4. A rotating rod 14 is fixedly connected to the center of the right side surface of the turntable 4. The other end of the rotating rod 14 is rotatably connected to the left side surface of the support plate 2. A drive gear 12 is fixedly connected to the outside of the drive rod 10. A driven gear 13 that meshes with the drive gear 12 is fixedly connected to the outside of the rotating rod 14. Multiple stranding holes 38 are opened through the left side surface of the turntable 4. A stranding frame 15 is fixedly installed on the left side surface of the turntable 4. Multiple mounting frames 22 are fixedly connected to the right side surface of the turntable 4. Each mounting frame 22 has an insert plate 23 inside. A raw yarn roller 24 is fixedly connected to the right side surface of each insert plate 23. When stranding the raw yarn is required, it is only necessary to first connect multiple... One end of the raw filament is wound around the outside of multiple raw filament rollers 24, and the other end of the multiple raw filaments is passed through the inside of multiple stranding holes 38. Then, the other end of the multiple raw filaments is passed through the inside of the stranding frame 15 and wound around the outside of the winding assembly. At this time, the first motor 3 starts to run. The first motor 3 drives the drive rod 10 to rotate synchronously. The drive rod 10 drives the drive gear 12 to rotate synchronously. The drive gear 12 then drives the driven gear 13 to rotate synchronously. The driven gear 13 then drives the rotating rod 14 and the turntable 4 to rotate synchronously. During the rotation of the turntable 4 and the stranding frame 15, the multiple raw filaments can be effectively stranded. At this time, the pitch carbon fiber can be produced.
[0038] In one embodiment, such as Figure 2 and Figure 4As shown, multiple mounting frames 22 are all fixedly connected to the outside of a fixing block 25. A fixing rod 26 is provided inside the fixing block 25. One end of the fixing rod 26 extends to the outside of the fixing block 25 and is fixedly connected to a pull plate. An abutment plate 27 is fixedly connected to the outside of the fixing rod 26. A return spring 28 is sleeved on the outside of the fixing rod 26, and the return spring 28 abuts against the abutment plate 27 and the fixing block 25. Guide grooves for the movement of the fixing rod 26 are provided on the contact surfaces of the fixing block 25 and the mounting frame 22. A guide groove for the movement of the fixing rod 26 is also provided inside the insert plate 23. When it is necessary to fix the yarn roller 24, simply pull the pull plate first. At this time, the pull plate will drive the fixing... The fixed rod 26 moves synchronously, and the fixed rod 26 then drives the contact plate 27 to move synchronously. During the movement of the contact plate 27, it will squeeze the return spring 28. At this time, the insert plate 23 is inserted into the inside of the mounting frame 22, and then the pull plate is released. At this time, the return spring 28 returns to its original position, driving the contact plate 27 and the fixed rod 26 to move synchronously. When the fixed rod 26 is inserted into the guide groove inside the insert plate 23, the insert plate 23 and the mounting frame 22 can be fixed. At this time, the raw yarn roller 24 can be fixedly installed, and it is also convenient for the workers to disassemble the raw yarn roller 24, so that the workers can easily wind the raw yarn onto the raw yarn roller 24.
[0039] In one embodiment, such as Figures 1-3 As shown, the winding assembly includes a fixed frame 7 fixedly connected to the left side of the upper surface of the base plate 1. A second motor 8 is fixedly connected to the front surface of the fixed frame 7. The output shaft of the second motor 8 is fixedly connected to a winding roller 9 through a coupling. The other end of the winding roller 9 is rotatably connected to the inner wall of the fixed frame 7. When it is necessary to wind up the asphalt carbon fiber, the second motor 8 starts to run. At this time, the second motor 8 will drive the winding roller 9 to rotate synchronously, so that the asphalt carbon fiber can be effectively wound up through the winding roller 9.
[0040] In one embodiment, such as Figures 1-3 As shown, mounting plates 5 are symmetrically arranged in the middle of the upper surface of the base plate 1, and guide rollers 6 are rotatably connected between the two mounting plates 5. The setting of guide rollers 6 can effectively improve the stability of the stranded raw yarn during the movement process.
[0041] In one embodiment, such as Figures 1-3As shown, an adjusting plate 16 is fixedly connected to the upper surface of the base plate 1. The adjusting plate 16 is located on the left side of the support plate 2. A third motor 17 is fixedly connected to the front surface of the adjusting plate 16. The output shaft of the third motor 17 is fixedly connected to a threaded rod 18 through a coupling. The other end of the threaded rod 18 is rotatably connected to the rear inner wall of the adjusting plate 16. A threaded block 19 is threadedly connected to the outside of the threaded rod 18. A guide groove for the threaded block 19 to move is opened on the upper surface of the adjusting plate 16. A traction frame 20 is fixedly connected to the upper surface of the threaded block 19. During the operation of the winding assembly, the third motor 17 will also start running synchronously. At this time, the third motor 17 will drive the threaded rod 18 to rotate in both directions. During the rotation of the threaded rod 18, the threaded block 19 will move synchronously outside the threaded rod 18, driving the traction frame 20 to move synchronously. At this time, the traction frame 20 can be used to traction the stranded raw yarn, so that the asphalt carbon fiber can be evenly wound around the outside of the winding roller 9.
[0042] In one embodiment, such as Figure 1 , Figure 2 , Figure 3 and Figure 5As shown, the cleaning assembly includes an L-shaped plate 21. The right side surface of the L-shaped plate 21 is fixedly connected to the left side surface of the threaded block 19. The left side surface of the adjusting plate 16 has a guide groove for the L-shaped plate 21 to move. A lower plate 29 is fixedly connected to the upper surface of the L-shaped plate 21. First side plates 30 are fixedly connected to the front and rear surfaces of the lower plate 29. An upper plate 31 is located directly above the lower plate 29. A handle is fixedly connected to the middle of the upper surface of the upper plate 31. Second side plates 32 are fixedly connected to the front and rear surfaces of the upper plate 31. A connecting rod 33 is fixedly connected to the middle of the upper surface of each of the two first side plates 30. A limiting plate 34 is fixedly connected to the other end of the connecting rod 33. A guide groove for the connecting rod 33 to move is opened through the middle of the upper surface of each of the two second side plates 32. A retaining spring 35 is sleeved on the outside of each of the two connecting rods 33. The two retaining springs 35 abut against the limiting plate 34 and the second side plates 32. Cleaning cotton 37 is attached to both sides of the upper plate 31 and the lower plate 29. When it is necessary to clean the outer surface of the asphalt carbon fiber, simply pull the handle. The handle will drive the upper plate 31 to move synchronously. The upper plate 31 will then drive the second side plate 32 to move synchronously outside the connecting rod 33. During the movement of the second side plate 32, the contact spring 35 will be squeezed. Then, the other end of the asphalt carbon fiber is wrapped around the outside of the take-up roller 9. Then, the pull plate is released. At this time, the contact spring 35 returns to its original position, driving the second side plate 32 and the upper plate 31 to move synchronously. During the operation of the take-up assembly, the asphalt carbon fiber will be stretched. During the stretching and movement of the asphalt carbon fiber, the cleaning cotton 37 can effectively clean the dust and other impurities adhering to the outside of the asphalt carbon fiber, thereby effectively improving the overall appearance and quality of the asphalt carbon fiber after production and effectively improving the overall practicality of the device.
[0043] In one embodiment, such as Figures 1-3 As shown, both connecting rods 33 are fitted with bellows covers 36. The two ends of the bellows covers 36 are fixedly connected to the opposite side of the limiting plate 34 and the second side plate 32, respectively. By setting the bellows covers 36, the abutment spring 35 can be effectively protected from dust, thereby effectively extending the service life of the abutment spring 35, without affecting the normal use of the abutment spring 35.
[0044] The above embodiment discloses a device for stranding pitch-carbon fiber precursors. When stranding pitch-carbon fiber precursors is required, one end of each precursor is first wound around the outside of multiple precursor rollers 24, then the other end of each precursor is passed through multiple stranding holes 38, and then the other end of each precursor is passed through the inside of a stranding frame 15 and wound around the outside of a take-up roller 9 (when winding the precursors around the take-up roller 9, the precursors need to be passed between two cleaning cotton balls 37 first). After the precursor winding is completed, the first motor 3 starts running, at which time the first motor 3 drives the turntable 4 to... The turntable 4 and the stranding frame 15 rotate synchronously, so that multiple raw filaments can be effectively stranded through the turntable 4 and the stranding frame 15. During the operation of the first motor 3, the second motor 8 will also start running synchronously. At this time, the asphalt carbon fiber can be stretched and wound by the winding roller 9. During the winding process of the stranded asphalt carbon fiber, the cleaning cotton 37 can effectively clean the dust and other impurities adhering to the surface of the asphalt carbon fiber, thereby effectively improving the overall appearance and quality of the asphalt carbon fiber after production and processing, and effectively improving the overall practicality of the device.
[0045] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.
Claims
1. A device for stranding pitch-carbon fiber precursor fibers, comprising a base plate (1), characterized in that, A support plate (2) is fixedly connected to the right side of the upper surface of the base plate (1). A connecting plate (11) is provided on the left side of the support plate (2). The bottom of the connecting plate (11) is fixedly connected to the upper surface of the base plate (1). A first motor (3) is fixedly connected to the right side of the support plate (2). The output shaft of the first motor (3) is fixedly connected to a drive rod (10) through a coupling. The other end of the drive rod (10) is rotatably connected to the right side of the connecting plate (11). A twisting assembly is disposed on the left side of the support plate (2) and is used to twist the raw yarn; The winding assembly is located on the left side of the upper surface of the base plate (1) and at the discharge end of the twisting assembly, and is used to wind up the twisted raw yarn. The cleaning component is located above the base plate (1) and to the right of the winding component, and is used to clean the surface of the stranded raw yarn. An adjusting plate (16) is fixedly connected to the upper surface of the base plate (1). The adjusting plate (16) is located on the left side of the support plate (2). A third motor (17) is fixedly connected to the front surface of the adjusting plate (16). The output shaft of the third motor (17) is fixedly connected to a threaded rod (18) through a coupling. The other end of the threaded rod (18) is rotatably connected to the rear inner wall of the adjusting plate (16). A threaded block (19) is threadedly connected to the outside of the threaded rod (18). A guide groove for the threaded block (19) to move is opened on the upper surface of the adjusting plate (16). A traction frame (20) is fixedly connected to the upper surface of the threaded block (19). The cleaning assembly includes an L-shaped plate (21), the right side surface of which is fixedly connected to the left side surface of a threaded block (19). A guide groove for the L-shaped plate (21) to move is provided on the left side surface of the adjusting plate (16). A lower plate (29) is fixedly connected to the upper surface of the L-shaped plate (21). First side plates (30) are fixedly connected to both the front and rear surfaces of the lower plate (29). An upper plate (31) is located directly above the lower plate (29). A handle is fixedly connected to the middle of the upper surface of the upper plate (31). Second side plates (32) are fixedly connected to both the front and rear surfaces of the upper plate (31). Connecting rods (33) are fixedly connected to the middle of the upper surfaces of both first side plates (30). The other end of the connecting rod (33) is fixedly connected to the limiting plate (34). The upper surface of the two second side plates (32) is provided with a guide groove for the connecting rod (33) to move through. The two connecting rods (33) are fitted with a retaining spring (35). The two retaining springs (35) abut against the limiting plate (34) and the second side plate (32). Cleaning cotton (37) is glued to the opposite side of the upper plate (31) and the lower plate (29).
2. The apparatus for stranding pitch-carbon fiber precursor fibers according to claim 1, characterized in that, The plying assembly includes a turntable (4), a rotating rod (14) is fixedly connected to the middle of the right side surface of the turntable (4), the other end of the rotating rod (14) is rotatably connected to the left side surface of the support plate (2), a drive gear (12) is fixedly connected to the outside of the drive rod (10), a driven gear (13) meshing with the drive gear (12) is fixedly connected to the outside of the rotating rod (14), a plurality of plying holes (38) are opened through the left side surface of the turntable (4), a plying frame (15) is fixedly installed on the left side surface of the turntable (4), a plurality of mounting frames (22) are fixedly connected to the right side surface of the turntable (4), each of the mounting frames (22) is provided with an insert plate (23), and a raw yarn roller (24) is fixedly connected to the right side surface of each of the insert plates (23).
3. The apparatus for stranding pitch-carbon fiber precursor fibers according to claim 2, characterized in that, A fixing block (25) is fixedly connected to the outside of each of the mounting frames (22). A fixing rod (26) is provided inside the fixing block (25). One end of the fixing rod (26) extends to the outside of the fixing block (25) and is fixedly connected to a pull plate. An abutment plate (27) is fixedly connected to the outside of the fixing rod (26). A return spring (28) is sleeved on the outside of the fixing rod (26). The return spring (28) abuts between the abutment plate (27) and the fixing block (25). A guide groove for the fixing rod (26) to move is opened on the contact surface between the fixing block (25) and the mounting frame (22). A guide groove for the fixing rod (26) to move is opened inside the insert plate (23).
4. The apparatus for stranding pitch-carbon fiber precursor fibers according to claim 1, characterized in that, The winding assembly includes a fixed frame (7) fixedly connected to the left side of the upper surface of the base plate (1). A second motor (8) is fixedly connected to the front surface of the fixed frame (7). The output shaft of the second motor (8) is fixedly connected to a winding roller (9) via a coupling. The other end of the winding roller (9) is rotatably connected to the inner wall of the fixed frame (7).
5. The apparatus for stranding pitch-carbon fiber precursor fibers according to claim 1, characterized in that, The upper surface of the base plate (1) is symmetrically provided with mounting plates (5), and guide rollers (6) are rotatably connected between the two mounting plates (5).
6. The apparatus for stranding pitch-carbon fiber precursor fibers according to claim 1, characterized in that, Both of the connecting rods (33) are fitted with bellows covers (36), and the two ends of the bellows covers (36) are fixedly connected to the opposite side of the limiting plate (34) and the second side plate (32).