A multi-stage sealing device for a pneumatic conveying fan shaft seal

Abstract

The utility model relates to sealed equipment technical field especially relates to a kind of multistage sealing equipment of pneumatic conveying fan shaft seal.It mainly aims at the packing type shaft seal used by pneumatic conveying fan of starch production line dehydration drying workshop cannot satisfy 0 leakage requirement, there is dust leakage to cause security risk and the problem that existing processing scheme maintenance is complicated, downtime is long, the following technical scheme is proposed, including fan body, the outer ring of the rotating shaft of fan body is provided with shaft seal, further including the collection mechanism installed in the side surface of fan body, the collection mechanism is located the outside of shaft seal for collecting leaked dust;Suction pipe connected on the collection mechanism, the other end of the suction pipe is connected with suction assembly, the suction assembly is installed in the side surface of fan body and with its inside intercommunication.The utility model can realize pneumatic conveying fan shaft seal 0 leakage to avoid security risk, reduce maintenance workload and downtime simultaneously, guarantee production line continuous high-efficiency operation.

Description

Technical Field

[0001] This utility model relates to the field of sealing equipment technology, and in particular to a multi-stage sealing device for a pneumatic conveying fan shaft seal. Background Technology

[0002] In the dehydration and drying workshop of a starch production line, the pneumatic conveying fan is a key piece of equipment for connecting the finished starch product to the subsequent packaging. The main function of this equipment is to mix the dried starch, whose moisture content has been reduced to below 14% after drying, with air to form a dust-like fluid. This fluid is then drawn into the fan through a conveying system consisting of a cyclone separator, an airlock, and a pneumatic conveying duct. The fan then provides the power to throw the material out at high speed along the air delivery duct.

[0003] However, in actual production and operation, the shaft seal of this pneumatic conveying blower suffers from severe dust leakage. Since starch dust is a flammable and explosive medium, shaft seal leakage not only wastes raw materials and pollutes the production environment, but also poses a significant safety hazard of dust explosion, seriously threatening the personal safety of on-site operators and the safety of production equipment and property. Therefore, the production site has imposed a stringent "zero leakage" sealing requirement on the equipment's shaft seal. Currently, existing pneumatic conveying blowers generally use a packing-type shaft seal structure. This type of shaft seal allows for minor leakage and cannot meet the "zero leakage" requirement in starch production scenarios. To alleviate the leakage problem, equipment manufacturers need to frequently tighten the packing gland and promptly replace worn-out packing, which not only increases equipment maintenance workload and downtime but also fails to fundamentally solve the leakage problem. Therefore, this utility model proposes a multi-stage sealing device for the shaft seal of a pneumatic conveying blower. Utility Model Content

[0004] The purpose of this invention is to address the problems in the background art where the packing-type shaft seal used in the pneumatic conveying fan of the starch production line dehydration and drying workshop cannot meet the zero leakage requirement, resulting in dust leakage and safety hazards, as well as the problems of cumbersome maintenance and long downtime of existing treatment solutions. The invention proposes a multi-stage sealing device for the shaft seal of the pneumatic conveying fan.

[0005] The technical solution of this utility model is as follows: A multi-stage sealing device for a pneumatic conveying fan shaft seal includes a fan body, a shaft seal being provided on the outer ring of the fan body's rotating shaft, and a collection mechanism installed on the side of the fan body, the collection mechanism being located outside the shaft seal for collecting leaked dust; a suction pipe connected to the collection mechanism, the other end of the suction pipe being connected to a suction assembly, the suction assembly being installed on the side of the fan body and communicating with its interior; a fixing mechanism fixed to the side of the fan body, the fixing mechanism being used to fix the suction assembly, realizing the connection between the suction assembly and the fan body; and a positioning component located above the suction assembly, the positioning component being installed on the side of the fixing mechanism for positioning the suction assembly.

[0006] Optionally, the collection mechanism includes two sets of symmetrically arranged fixing rings. The fixing rings are semi-circular and have through holes. A screw fixed to the side of the fan body passes through the through holes. A collection cover is fixedly connected to the side of the fixing ring away from the fan body. A combination plate is fixedly connected to both ends of the collection cover. The two sets of combination plates on the same side are connected by fasteners.

[0007] Optionally, each of the two sets of fixing rings has an installation groove on the side near the fan body, and a first sealing ring is installed in the two sets of installation grooves.

[0008] Optionally, the collection mechanism further includes a discharge pipe, which is fixedly connected to and communicates with the inner side of a set of collection hoods. The discharge pipe is arranged in the tangential direction of the collection hoods and is connected to a suction pipe.

[0009] Optionally, the suction assembly includes a connecting pipe connected to the suction pipe, an installation pipe fixedly connected to the end of the connecting pipe away from the suction pipe, a retaining ring sleeved on the outer ring of the end of the installation pipe away from the connecting pipe, and a second sealing ring provided between the retaining ring and the blower body.

[0010] Optionally, the mounting tube is flared, and the diameter of the end of the mounting tube near the connecting tube is smaller than the diameter of the end near the retaining ring.

[0011] Optionally, the fixing mechanism includes a fixing plate fixedly connected to the side of the fan body, a positioning plate fixedly connected to the side of the fixing plate away from the fan body, and a pressing plate provided on the side of the positioning plate close to the fan body. The pressing plate is slidably connected in the fixing plate. The fixing plate, positioning plate and pressing plate are all U-shaped. The pressing plate is located on the side of the retaining ring away from the fan body.

[0012] Optionally, four sets of sliding rods are fixedly connected to the side of the extrusion plate near the positioning plate. The sliding rods pass through the positioning plate and slide with it. Two sets of movable plates are provided on the side of the positioning plate away from the extrusion plate. The two sets of movable plates are respectively passed through by the two sets of sliding rods. A threaded rod is provided in the middle of the movable plate away from the positioning plate. One end of the threaded rod is fixedly connected to the positioning plate. A nut is threaded onto the threaded rod. A synchronization ring is sleeved on the outer ring of the sliding rod. The synchronization ring is located between the positioning plate and the movable plate.

[0013] Optionally, the positioning component includes two sets of mounting blocks fixedly connected to the side of the positioning plate away from the fan body. A fixed shaft is fixedly connected to each of the two sets of mounting blocks, and a rotating plate is rotatably connected to the fixed shaft. A clamping plate is provided above the rotating plate. The clamping plate is L-shaped and fixedly connected to the positioning plate.

[0014] Optionally, a threaded sleeve is fixedly connected to the rotating plate, a bolt is threaded into the threaded sleeve, a pressure block is provided below the bolt, and multiple sets of limiting rods are fixedly connected to the top of the pressure block. The limiting rods pass through the rotating plate and are fixedly connected to a limiting disc.

[0015] In summary, this application includes at least one of the following beneficial technical effects: This utility model forms a dust collection space around the shaft seal through a collection mechanism. Combined with the Laval nozzle principle of the suction component to generate negative pressure, the leaked dust is sucked into the fan body through the discharge pipe and suction pipe. With the multiple seals of the first sealing ring and the second sealing ring, the problem of shaft seal leakage is fundamentally solved, the risk of dust explosion is avoided, and the stringent safety requirement of zero leakage is met. Furthermore, the suction assembly is quickly assembled by fixing the ring screw nut. The suction assembly is quickly fixed and positioned by using the fixing mechanism nut, extrusion plate and positioning assembly. The overall installation does not require long-term downtime, which greatly shortens the maintenance time and ensures the conveying capacity of the starch production line. In summary, this utility model can achieve zero leakage of the shaft seal of the pneumatic conveying fan to avoid safety hazards, while reducing maintenance workload and downtime, and ensuring continuous and efficient operation of the production line. Attached Figure Description

[0016] Figure 1 This is a structural schematic diagram of a multi-stage sealing device for a pneumatic conveying fan shaft seal; Figure 2 This is a schematic diagram of the collection mechanism; Figure 3 This is a schematic diagram of the suction assembly. Figure 4 yes Figure 1 Enlarged view of point A in the middle; Figure 5 This is a schematic diagram of the structure after the positioning component is opened.

[0017] Figure label: 1. Fan body; 11. Shaft; 2. Collection mechanism; 21. Fixing ring; 22. Collection cover; 23. Combination plate; 24. Mounting groove; 25. First sealing ring; 26. Discharge pipe; 3. Suction tube; 4. Suction assembly; 41. Connecting tube; 42. Mounting tube; 43. Snap ring; 44. Second sealing ring; 5. Fixing mechanism; 51. Fixing plate; 52. Positioning plate; 53. Pressing plate; 54. Slide rod; 55. Moving plate; 56. Threaded rod; 57. Nut; 58. Synchronizing ring; 6. Positioning component; 61. Mounting block; 62. Fixed shaft; 63. Rotating plate; 64. Clamping plate; 65. Threaded sleeve; 66. Bolt; 67. Pressure block; 68. Limiting rod; 69. Limiting disc. Detailed Implementation

[0018] The technical solution of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of this utility model, but not all embodiments.

[0019] The components of the present invention embodiments described and shown in the accompanying drawings can typically be arranged and designed in a variety of different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention.

[0020] Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this utility model.

[0021] In the description of this utility model, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings and are only for the convenience of describing this utility model 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 utility model. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0022] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" 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 or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0023] like Figure 1 and Figure 2As shown, this utility model proposes a multi-stage sealing device for a pneumatic conveying fan shaft seal, including a fan body 1, a shaft seal on the outer ring of the rotating shaft 11 of the fan body 1, and a collection mechanism 2 installed on the side of the fan body 1. The collection mechanism 2 is located outside the shaft seal and is used to collect leaked dust. The collection mechanism 2 includes two sets of symmetrically arranged fixing rings 21. The fixing rings 21 are semi-circular and have through holes. A screw welded to the side of the fan body 1 passes through the through holes. The fixing rings 21 are fixed to the side of the fan body 1 by tightening nuts onto the screws. A collection cover 22 is fixedly connected to the side of the fixing rings 21 away from the fan body 1. A combination plate 23 is fixedly connected to both ends of the collection cover 22. The two sets of combination plates 23 on the same side are connected by fasteners. After the combination plates 23 are connected by fasteners, they form a whole and are clamped to the outside of the rotating shaft 11. Two sets of fixing rings 21 are respectively provided with mounting grooves 24 on the side near the fan body 1. A first sealing ring 25 is installed in the two sets of mounting grooves 24. The first sealing ring 25 increases the sealing performance and prevents dust from leaking through the gap between the fixing rings 21 and the fan body 1. The collection mechanism 2 also includes a discharge pipe 26, which is fixedly connected to a set of collection covers 22 and communicates with their inner side. The discharge pipe 26 is set in the tangential direction of the collection covers 22 and is connected to the suction pipe 3, so that the dust can be sucked out when suction is generated. Outside air enters through the gap between the collection covers 22 and the rotating shaft 11.

[0024] Furthermore, such as Figure 3 As shown, the sealing device also includes a suction pipe 3 connected to the collection mechanism 2. The other end of the suction pipe 3 is connected to a suction assembly 4. A through hole corresponding to the suction assembly 4 is opened on the side of the fan body 1. The suction assembly 4 is installed on the side of the fan body 1 and communicates with the inside of the fan body 1 through the through hole. The suction assembly 4 includes a connecting pipe 41 connected to the suction pipe 3. An installation pipe 42 is fixedly connected to the end of the connecting pipe 41 away from the suction pipe 3. A retaining ring 43 is fitted around the outer ring of the end of the installation pipe 42 away from the connecting pipe 41. A second sealing ring 44 is provided between the retaining ring 43 and the fan body 1. The installation pipe 42 is flared. The diameter of the end of the installation pipe 42 near the connecting pipe 41 is smaller than the diameter of the end near the retaining ring 43. The shape of the installation pipe 42 forms a Laval nozzle principle. When the fan body 1 is working, the suction assembly 4 and the suction pipe 3 extract the dust leaking from the shaft seal position in the collection mechanism 2. At the same time, due to the change in the diameter of the installation pipe 42, the gas flow velocity in the suction pipe 3 is greater than the gas flow velocity in the installation pipe 42, thereby improving the efficiency of dust extraction.

[0025] For details, please refer to Figure 4 and Figure 5The sealing device also includes a fixing mechanism 5 fixed to the side of the blower body 1. The fixing mechanism 5 is used to fix the suction assembly 4, realizing the connection between the suction assembly 4 and the blower body 1. The fixing mechanism 5 includes a fixing plate 51 welded to the side of the blower body 1. A positioning plate 52 is fixedly connected to the side of the fixing plate 51 away from the blower body 1, and the positions of the fixing plate 51 and the positioning plate 52 are fixed. A pressing plate 53 is provided on the side of the positioning plate 52 near the blower body 1. The pressing plate 53 is slidably connected to the fixing plate 51. The fixing plate 51, the positioning plate 52, and the pressing plate 53 are all U-shaped to facilitate the sliding of the suction assembly 4 into the fixing mechanism 5. The pressing plate 53 is located on the side of the retaining ring 43 away from the blower body 1. When the pressing plate 53 is close to the blower body 1, it presses and fixes the retaining ring 43. Four sets of sliding rods 54 are fixedly connected to the side of the pressing plate 53 near the positioning plate 52. The sliding rods 54 pass through the positioning plate 52 and slide with it. The limiting effect of the sliding rods 54 makes the movement of the pressing plate 53 smooth. Two sets of movable plates 55 are arranged on the side of the positioning plate 52 away from the extrusion plate 53. Each set of movable plates 55 is penetrated by two sets of sliding rods 54. A threaded rod 56 passes through the middle of each movable plate 55, away from the positioning plate 52. One end of the threaded rod 56 is fixedly connected to the positioning plate 52, and a nut 57 is threaded onto the threaded rod 56. When the nut 57 rotates, it moves along the length of the threaded rod 56. After tightening, the nut 57 moves the movable plate 55 closer to the positioning plate 52. A synchronization ring 58 is fitted around the outer ring of the sliding rod 54, located between the positioning plate 52 and the movable plate 55. When the movable plate 55 approaches the positioning plate 52, it moves the sliding rod 54 via the synchronization ring 58, thereby moving the extrusion plate 53 closer to the fan body 1, where it is fixed by the clamping ring 43. The arrangement of the movable plate 55, with its middle position away from the positioning plate 52, facilitates the application of pressure to the two sets of synchronization rings 58.

[0026] Furthermore, the aforementioned sealing device also includes a positioning component 6 located above the suction assembly 4. The positioning component 6 is installed on the side of the fixing mechanism 5 to position the suction assembly 4. The positioning component 6 includes two sets of mounting blocks 61 fixedly connected to the side of the positioning plate 52 away from the fan body 1. A fixed shaft 62 is fixedly connected to the two sets of mounting blocks 61. A rotating plate 63 is rotatably connected to the fixed shaft 62. The rotating plate 63 rotates around the fixed shaft 62 and slides on the fixed shaft 62. A retaining plate 64 is provided above the rotating plate 63. The retaining plate 64 is L-shaped and fixedly connected to the positioning plate 52. The L-shaped design of the retaining plate 64 prevents the rotating plate 63 from moving away from the positioning plate 52 when it is engaged with the retaining plate 64. A threaded sleeve 65 is fixedly connected to the rotating plate 63. A bolt 66 is threadedly connected to the threaded sleeve 65. The bolt 66 moves along its own length direction when rotating. A pressure block 67 is provided below the bolt 66. When the bolt 66 moves downward, it presses the pressure block 67 onto the mounting tube 42 to prevent the mounting tube 42 from shifting. Multiple sets of limiting rods 68 are fixedly connected to the top of the pressure block 67, ensuring smooth movement of the pressure block 67. The limiting rods 68 pass through the rotating plate 63 and are fixedly connected to a limiting disc 69, preventing the pressure block 67 from detaching.

[0027] In this embodiment, firstly, a collection mechanism 2 is installed on the outer side of the shaft seal of the rotating shaft 11 of the fan body 1 using two sets of semi-circular annular fixing rings 21. The through holes of the fixing rings 21 are aligned with the screws welded to the side of the fan body 1, and the nuts are tightened to make the fixing rings 21 fit tightly against the fan body 1. At this time, the first sealing ring 25 in the mounting groove 24 on the side of the fixing rings 21 closest to the fan body 1 is compressed, effectively preventing dust leakage through the gap between the fixing rings 21 and the fan body 1. Subsequently, the two end plates 23 of the collection cover 22 are connected as a whole using fasteners, so that the collection cover 22 is stably clamped on the outside of the rotating shaft 11, forming a dust collection space surrounding the shaft seal.

[0028] The suction assembly 4 is slidably embedded into the space formed by the U-shaped fixing plate 51, the positioning plate 52, and the extrusion plate 53. At this time, the installation tube 42 of the suction assembly 4 is aligned with the through hole on the side of the fan body 1. Then, the nut 57 on the threaded rod 56 on the outer side of the positioning plate 52 is rotated. The nut 57 moves along the threaded rod 56 and pushes the moving plate 55 closer to the positioning plate 52. The moving plate 55 drives the sliding rod 54 to slide through the synchronous ring 58, thereby causing the extrusion plate 53 to move towards the fan body 1. The extrusion plate 53 extrudes the retaining ring 43 to achieve a firm fixation of the suction assembly 4, so that the retaining ring 43 on the outer ring of the installation tube 42 and the second sealing ring 44 between the fan body 1 are tightly fitted. Afterward, the rotating plate 63 on the fixed shaft 62 in the positioning assembly 6 is rotated so that it is engaged under the L-shaped retaining plate 64. The bolt 66 in the threaded sleeve 65 is rotated. The bolt 66 pushes the pressure block 67 down and presses it tightly against the installation tube 42. Under the guiding and limiting action of the limiting rod 68 and the limiting plate 69, the installation tube 42 is prevented from shifting during operation.

[0029] During operation, the airflow inside the fan body 1 flows through the installation pipe 42 of the suction assembly 4. Since the installation pipe 42 is funnel-shaped, according to the Laval nozzle principle, the gas velocity in the suction pipe 3 is greater than that in the installation pipe 42, creating a negative pressure environment between the suction pipe 3 and the collection mechanism 2. If dust leaks at the shaft seal, the leaked dust will be intercepted by the collection hood 22 and collected in the collection space. Under negative pressure, it will enter the suction pipe 3 through the discharge pipe 26 tangential to the collection hood 22, and then be drawn into the fan body 1 through the connecting pipe 41 and the installation pipe 42 of the suction assembly 4. At the same time, outside air enters the collection space through the gap between the collection hood 22 and the rotating shaft 11, forming a continuous and stable negative pressure suction cycle, ultimately achieving a zero-leakage sealing effect at the shaft seal.

[0030] The above specific embodiments are merely optional embodiments of this utility model. Based on the technical solution of this utility model and the relevant teachings of the above embodiments, those skilled in the art can make various alternative improvements and combinations to the above specific embodiments.

Claims

1. A multi-stage sealing device for a pneumatic conveying fan shaft seal, comprising a fan body (1), wherein a shaft seal is provided on the outer ring of the rotating shaft (11) of the fan body (1), characterized in that, Also includes: A collection mechanism (2) is installed on the side of the fan body (1). The collection mechanism (2) is located outside the shaft seal and is used to collect leaked dust. A suction pipe (3) is connected to the collection mechanism (2), and a suction assembly (4) is connected to the other end of the suction pipe (3). The suction assembly (4) is installed on the side of the fan body (1) and communicates with its interior. A fixing mechanism (5) is fixed to the side of the fan body (1). The fixing mechanism (5) is used to fix the suction assembly (4) and realize the connection between the suction assembly (4) and the fan body (1). A positioning component (6) is located above the suction component (4). The positioning component (6) is installed on the side of the fixing mechanism (5) for positioning the suction component (4).

2. The multi-stage sealing device for a pneumatic conveying fan shaft seal according to claim 1, characterized in that, The collection mechanism (2) includes two sets of symmetrically arranged fixing rings (21). The fixing rings (21) are semi-circular rings with through holes. A screw fixed to the side of the fan body (1) is inserted through the through holes. A collection cover (22) is fixedly connected to the side of the fixing rings (21) away from the fan body (1). A combination plate (23) is fixedly connected to both ends of the collection cover (22). The two sets of combination plates (23) on the same side are connected by fasteners.

3. The multi-stage sealing device for a pneumatic conveying fan shaft seal according to claim 2, characterized in that, The two sets of fixing rings (21) are respectively provided with mounting grooves (24) on the side near the fan body (1), and the two sets of mounting grooves (24) are provided with first sealing rings (25).

4. The multi-stage sealing device for a pneumatic conveying fan shaft seal according to claim 3, characterized in that, The collection mechanism (2) further includes a discharge pipe (26), which is fixedly connected to a set of collection covers (22) and communicates with their inner side. The discharge pipe (26) is located in the tangential direction of the collection covers (22) and is connected to the suction pipe (3).

5. A multi-stage sealing device for a pneumatic conveying fan shaft seal according to claim 4, characterized in that, The suction assembly (4) includes a connecting pipe (41) connected to the suction pipe (3). An installation pipe (42) is fixedly connected to one end of the connecting pipe (41) away from the suction pipe (3). A retaining ring (43) is sleeved on the outer ring of the one end of the installation pipe (42) away from the connecting pipe (41). A second sealing ring (44) is provided between the retaining ring (43) and the fan body (1).

6. A multi-stage sealing device for a pneumatic conveying fan shaft seal according to claim 5, characterized in that, The mounting tube (42) is flared, and the diameter of the end of the mounting tube (42) near the connecting tube (41) is smaller than the diameter of the end near the retaining ring (43).

7. A multi-stage sealing device for a pneumatic conveying fan shaft seal according to claim 6, characterized in that, The fixing mechanism (5) includes a fixing plate (51) fixedly connected to the side of the fan body (1). A positioning plate (52) is fixedly connected to the side of the fixing plate (51) away from the fan body (1). A pressing plate (53) is provided on the side of the positioning plate (52) close to the fan body (1). The pressing plate (53) is slidably connected in the fixing plate (51). The fixing plate (51), the positioning plate (52) and the pressing plate (53) are all U-shaped. The pressing plate (53) is located on the side of the retaining ring (43) away from the fan body (1).

8. A multi-stage sealing device for a pneumatic conveying fan shaft seal according to claim 7, characterized in that, Four sets of sliding rods (54) are fixedly connected to the side of the extrusion plate (53) near the positioning plate (52). The sliding rods (54) pass through the positioning plate (52) and slide with it. Two sets of moving plates (55) are provided on the side of the positioning plate (52) away from the extrusion plate (53). The two sets of moving plates (55) are respectively passed through by the two sets of sliding rods (54). The middle position of the moving plate (55) is away from the positioning plate (52) and is provided with a threaded rod (56). One end of the threaded rod (56) is fixedly connected to the positioning plate (52). A nut (57) is threaded on the threaded rod (56). A synchronization ring (58) is sleeved on the outer ring of the sliding rod (54). The synchronization ring (58) is located between the positioning plate (52) and the moving plate (55).

9. A multi-stage sealing device for a pneumatic conveying fan shaft seal according to claim 8, characterized in that, The positioning component (6) includes two sets of mounting blocks (61) fixedly connected to the side of the positioning plate (52) away from the fan body (1). A fixed shaft (62) is fixedly connected to the two sets of mounting blocks (61). A rotating plate (63) is rotatably connected to the fixed shaft (62). A clamping plate (64) is provided above the rotating plate (63). The clamping plate (64) is L-shaped and fixedly connected to the positioning plate (52).

10. A multi-stage sealing device for a pneumatic conveying fan shaft seal according to claim 9, characterized in that, A threaded sleeve (65) is fixedly connected to the rotating plate (63), and a bolt (66) is threadedly connected to the threaded sleeve (65). A pressure block (67) is provided below the bolt (66), and multiple sets of limiting rods (68) are fixedly connected to the top of the pressure block (67). The limiting rods (68) pass through the rotating plate (63) and are fixedly connected to a limiting plate (69).

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