A continuous galvanizing apparatus for a steel strip

Abstract

The utility model provides a kind of strip steel continuous galvanizing device, a kind of strip steel continuous galvanizing device, including zinc pool, still include zinc plating assembly, surface flatness subassembly and pull-up subassembly, zinc plating assembly is arranged in zinc pool, the discharge end of upstream process is connected to one end of zinc pool, surface flatness subassembly and pull-up subassembly are sequentially arranged along the advancing direction of strip steel to the other end of zinc pool, zinc plating assembly is used for even zinc plating on strip steel surface, surface flatness subassembly is used for the zinc layer of strip steel surface, pull-up subassembly is used for pulling after strip steel of zinc plating.The utility model discloses a kind of strip steel continuous galvanizing device, pull-up subassembly is arranged, strip steel after zinc plating can be pulled to be higher, zinc layer can be cooled in the process of traction, strip steel can also be straightened, can accelerate the cooling speed of zinc liquid, better and downstream process butt joint, vertically arrange the device to reduce floor area, improve plant space utilization.

Description

Technical Field

[0001] This utility model belongs to the field of hot-dip galvanizing technology for steel strips, and in particular relates to a continuous galvanizing device for steel strips. Background Technology

[0002] Hot-dip galvanizing of steel is a process technology that improves the corrosion resistance of steel strips by immersing them in molten zinc to form a zinc alloy coating on the surface of the steel strips. It has a wide range of important applications in the industrial field.

[0003] With the rapid development of modern industry, strip steel, as an important type of steel, is widely used in many fields such as construction, automobile manufacturing, home appliance production, and transportation. These applications often place high demands on the corrosion resistance of strip steel. In the construction field, strip steel used for roofs and walls is exposed to wind, sun, and rain for a long time, making it prone to rust. In automobile manufacturing, strip steel used for body, chassis, and other components needs to withstand corrosion under various complex road conditions. Hot-dip galvanizing can significantly improve the corrosion resistance of strip steel and extend its service life. Therefore, the demand for hot-dip galvanizing of strip steel is increasing. In the existing strip steel galvanizing process, there are problems such as uneven galvanizing thickness, untimely cooling leading to poor connection with subsequent processes, and large footprint of strip steel galvanizing equipment, which cannot effectively utilize vertical space. Therefore, a new type of continuous strip steel galvanizing equipment is needed to solve the problem of large footprint of strip steel galvanizing equipment. Utility Model Content

[0004] In view of this, the present invention aims to provide a continuous strip galvanizing device to solve the problem of large footprint of strip galvanizing devices.

[0005] To achieve the above objectives, the technical solution of this utility model is implemented as follows: A continuous strip galvanizing apparatus includes a galvanizing tank disposed below a foundation, and further includes a galvanizing component, a surface leveling component, and a lifting component. The galvanizing component is disposed inside the galvanizing tank. One end of the galvanizing tank is connected to the discharge end of the upstream process, and the other end of the galvanizing tank is sequentially connected to the surface leveling component and the lifting component along the traveling direction of the strip. The galvanizing component is used to uniformly galvanize the surface of the strip, the surface leveling component is used to level the zinc layer on the surface of the strip, and the lifting component is used to lift the galvanized strip.

[0006] Furthermore, the galvanizing assembly includes a first roller and a second roller, with multiple first rollers and multiple second rollers sequentially arranged in the galvanizing bath along the strip's travel direction; the outer periphery of the first roller is rolled to the upper surface of the strip, and the outer periphery of the second roller is rolled to the lower surface of the strip, with the first rollers and second rollers arranged alternately in the galvanizing bath.

[0007] Furthermore, the galvanizing assembly also includes a guide roller shaft, which is rotatably arranged inside the galvanizing bath. The guide roller shaft is a drum-shaped roller and is used to guide the strip steel out of the galvanizing bath.

[0008] Furthermore, the surface smoothing component includes a frame, two scrapers, and two sets of air knives. The frame is installed at the upper end of the galvanizing tank, and two scrapers are installed inside the frame. The two scrapers are located on both sides of the strip steel and are arranged opposite each other. The scraping end of each scraper abuts against one side of the strip steel, and a set of air knives is installed above each scraper.

[0009] Furthermore, the air knife includes an air jet frame, a nozzle, and an air inlet pipe. Multiple air jet frames are installed on the frame, and multiple nozzles are installed in each air jet frame. The air jet end of the nozzle faces the strip steel, and the air inlet end of the nozzle is connected to one end of the air inlet pipe. The air inlet pipe is installed inside the frame, and the other end of the air inlet pipe is connected to an external high-pressure air pump.

[0010] Furthermore, the stretching assembly includes a bracket and a third roller shaft. The bracket is provided on one side of the galvanizing tank, the third roller shaft is rotatably connected inside the bracket, and the lower surface of the strip is rolledly connected to the outer periphery of the third roller shaft. The bracket has two parallel fourth rollers rotatably connected inside. The two fourth rollers are arranged longitudinally, and the strip is rolled around the outside of the two fourth rollers. One of the fourth rollers is connected to the output end of the drive unit, and the fixed end of the drive unit is installed on the outside of the bracket.

[0011] Furthermore, a pressure roller is rotatably connected inside the bracket. The pressure roller is located above the fourth roller shaft at the uppermost end, and its outer periphery is rotatably connected to the upper surface of the strip.

[0012] Furthermore, the drive unit includes a servo motor, a synchronous belt, and a synchronous pulley. The servo motor is mounted on the lower end of the bracket. The output wheel of the servo motor and the synchronous pulley are sleeved with a synchronous belt to form a synchronous transmission structure. The synchronous pulley is fixedly sleeved on one end of any fourth roller shaft.

[0013] Compared with the prior art, the continuous strip galvanizing device of this utility model has the following advantages: (1) The continuous galvanizing device for strip steel described in this utility model is equipped with a lifting component, which can pull the galvanized strip steel to a higher position. During the pulling process, the zinc layer can be cooled and the strip steel can be straightened, which can accelerate the cooling speed of the zinc liquid and better connect with the downstream process. The vertical layout of the device reduces the floor space and improves the utilization rate of the factory space.

[0014] (2) The continuous galvanizing device for strip steel described in this utility model has a first roller and a second roller arranged in an alternating manner, which makes the strip steel form a tortuous path in the zinc liquid, increases the contact area and contact time between the strip steel and the zinc liquid, avoids the problem of insufficient contact in some parts of the strip steel causing incomplete galvanizing or excessively thin coating, and also allows the zinc layer on the surface of the strip steel to adhere evenly, reducing the generation of defects such as bubbles and zinc nodules.

[0015] (3) The continuous galvanizing device for strip steel described in this utility model is equipped with a guide roller shaft. Through rolling contact with the strip steel, the strip steel can be discharged from the galvanizing bath, avoiding the strip steel from shifting due to gravity or tension when leaving the zinc liquid. The lateral constraint effect generated by its drum-shaped structure can effectively correct the slight deviation that may occur in the strip steel during the galvanizing process.

[0016] (3) The continuous galvanizing device for strip steel described in this utility model is equipped with a scraper, which can initially flatten the zinc layer, reduce the processing burden of subsequent air knife, and also realize the recycling of zinc material.

[0017] (4) The continuous galvanizing device for strip steel described in this utility model is equipped with an air knife, which can eliminate the difference in zinc layer thickness that still exists after scraper treatment, avoid product defects caused by uneven zinc layer, and the cooling effect of airflow can make the zinc layer solidify quickly, reducing the natural flow deformation of the zinc layer under gravity.

[0018] (5) The continuous galvanizing device for strip steel described in this utility model wraps the galvanized strip steel between the fourth roller shafts to prevent the strip steel from falling due to gravity during the lifting process. It can also flatten the zinc layer on the surface of the strip steel, reduce safety hazards, improve production efficiency, and increase the yield rate. Attached Figure Description

[0019] The accompanying drawings, which form part of this utility model, are used to provide a further understanding of the utility model. The illustrative embodiments of the utility model and their descriptions are used to explain the utility model and do not constitute an undue limitation of the utility model. In the drawings: Figure 1 This is a schematic diagram of the overall structure of a continuous strip galvanizing device according to an embodiment of the present utility model; Figure 2 This is a schematic diagram of the galvanized component described in an embodiment of the present utility model; Figure 3 This is a schematic diagram of the first roller shaft and the second roller shaft according to an embodiment of the present utility model; Figure 4 This is a schematic diagram of the surface smoothing component described in an embodiment of the present utility model; Figure 5 This is a schematic diagram of the air knife described in an embodiment of the present utility model; Figure 6 This is a schematic diagram of the lifting component described in an embodiment of the present utility model; Figure 7 This is a schematic diagram of the drive unit described in an embodiment of the present utility model.

[0020] Explanation of reference numerals in the attached figures: 1-Galvanizing tank; 2-Galvanizing assembly; 21-First roller; 22-Second roller; 23-Guide roller; 3-Surface leveling assembly; 31-Frame; 32-Scraper; 33-Air knife; 331-Air jet frame; 332-Nozzle; 333-Air inlet pipe; 4-Lifting assembly; 41-Support; 42-Third roller; 43-Fourth roller; 44-Drive unit; 45-Pressure roller; 441-Servo motor; 442-Synchronous belt; 443-Synchronous pulley; 5-Strip steel. Detailed Implementation

[0021] It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0022] In the description of this utility model, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing this 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," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this utility model, unless otherwise stated, "a plurality of" means two or more.

[0023] 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.

[0024] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0025] like Figure 1As shown, a continuous strip galvanizing device includes a galvanizing tank 1, a galvanizing component 2, a surface leveling component 3, and a lifting component 4. The galvanizing component 2 is installed inside the galvanizing tank 1. One end of the galvanizing tank 1 is connected to the discharge end of the upstream process. The surface leveling component 3 and the lifting component 4 are arranged sequentially along the traveling direction of the strip 5 at the other end of the galvanizing tank 1. The galvanizing component 2 is used to uniformly galvanize the surface of the strip 5, the surface leveling component 3 is used to level the zinc layer on the surface of the strip 5, and the lifting component 4 is used to lift the galvanized strip 5.

[0026] like Figure 2 As shown, the galvanizing assembly 2 includes a first roller 21 and a second roller 22. Multiple first rollers 21 and multiple second rollers 22 are sequentially arranged in the galvanizing bath 1 along the traveling direction of the strip steel 5. The outer periphery of the first roller 21 is rolled to the upper surface of the strip steel 5, and the outer periphery of the second roller 22 is rolled to the lower surface of the strip steel 5. The first rollers 21 and the second rollers 22 are arranged alternately in the galvanizing bath 1. The first roller 21 is rolled to the upper surface of the strip 5, and the second roller 22 is rolled to the lower surface of the strip 5. The two are arranged in an alternating manner in the galvanizing bath 1. This alternating arrangement causes the strip 5 to form a wave-shaped travel trajectory in the galvanizing bath, which prolongs the contact time between the strip and the zinc liquid and ensures that the surface of the strip can be fully wetted by the zinc liquid. During the travel of the strip 5, the first roller 21 and the second roller 22 rotate synchronously with the strip 5, guiding the strip 5 through the galvanizing bath 1 along a preset path. After the strip 5 conveyed by the upstream process enters the galvanizing bath 1, it first contacts the second roller 22 below, and then is pressed into the depth of the zinc liquid by the first roller 21 above. Then, the immersion angle of the strip 5 is continuously changed by the subsequent alternating first roller 21 and second roller 22, which prolongs the residence time of the strip 5 in the galvanizing bath 1. The staggered arrangement of the first roller 21 and the second roller 22 creates a tortuous path for the strip steel 5 in the zinc bath, increasing the contact area and contact time between the strip steel 5 and the zinc bath. This avoids problems such as incomplete plating or excessively thin plating caused by insufficient contact in some areas of the strip steel 5, and also allows the zinc layer on the surface of the strip steel 5 to adhere evenly, reducing the generation of defects such as bubbles and zinc nodules.

[0027] like Figure 3As shown, it also includes a guide roller shaft 23. The guide roller shaft 23 is rotatably installed inside the galvanizing bath 1. The guide roller shaft 23 is a drum-shaped roller and is used to guide the strip steel 5 out of the galvanizing bath 1. When the strip steel 5 enters the guide roller shaft 23, it is guided in direction through rolling contact with the outer periphery of the guide roller shaft 23. Since the guide roller shaft 23 is a drum-shaped roller, when the strip steel 5 rolls on its surface, the arc-shaped structure of the roller surface will generate a lateral constraint force, ensuring that the strip steel always moves along the central axis and is eventually smoothly exited from the galvanizing bath 1 and enters the subsequent surface leveling assembly 3. The guide roller shaft is set up so that the strip steel 5 can be exported from the galvanizing bath 1 through rolling contact with the strip steel 5, avoiding the strip steel from deviating due to gravity or tension when leaving the zinc liquid. The lateral constraint effect generated by its drum-shaped structure can effectively correct the slight deviation that may occur in the strip steel 5 during the galvanizing process.

[0028] like Figure 4 As shown, the surface leveling component 3 includes a frame 31, two scrapers 32, and two sets of air knives 33. The frame 31 is installed at the upper end of the galvanizing bath 1. Two scrapers 32 are installed inside the frame 31, located on both sides of the strip steel 5 and facing each other. The scraping end of each scraper 32 abuts against one side of the strip steel 5. A set of air knives 33 is installed above each scraper 32. When the strip steel 5, after being immersed in the galvanizing bath 1, is discharged and enters the surface leveling component 3, the zinc layer attached to the surface of the strip steel 5 is not yet complete. After complete solidification, the strip steel 5 passes between two scrapers 32 along the travel direction. The scraping end of the scraper 32 is in close contact with the surface of the strip steel 5. The excess zinc layer on the surface of the strip steel is scraped off by mechanical scraping, and the residual zinc layer is smoothed out. Since the scraper 32 is located below the air knife 33, the excess zinc material scraped off can fall back into the galvanizing bath 1 under the action of gravity, realizing the recycling of zinc material. The scraper 32 can initially smooth the zinc layer, reduce the processing burden of the subsequent air knife, and also realize the recycling of zinc material.

[0029] like Figure 5As shown, the air knife 33 includes an air jet frame 331, nozzles 332, and an air inlet pipe 333. Multiple air jet frames 331 are mounted on the frame 31, and multiple nozzles 332 are installed within each air jet frame 331. The air jet ends of the nozzles 332 face the strip 5, and the air inlet ends of the nozzles 332 are connected to one end of the air inlet pipe 333. The air inlet pipe 333 is located within the frame, and its other end is connected to an external high-pressure air pump. The high-pressure air pump is existing technology, and its model is RB-71D-2. After the strip 5 is initially leveled by the scraper 32, it enters the air knife 33 along the travel direction. At this time, the air inlet pipe 333 guides the compressed air supplied by the high-pressure air pump into the air jet frame 331, which then forms a high-speed airflow through the multiple nozzles 332 within the air jet frame 331, spraying it towards the surface of the strip 5. High-speed airflow acts on the zinc layer on the surface of strip steel 5 that is not completely solidified. The airflow pressure further smooths the zinc layer and blows away the small amount of excess zinc material remaining after the scraper 32 treatment, making the zinc layer thickness on the surface of strip steel 5 more uniform. This can eliminate the slight unevenness or thickness difference that still exists after the scraper 32 treatment, avoid product defects caused by uneven zinc layer, and the cooling effect of the airflow can make the zinc layer solidify quickly, reducing the natural flow deformation of the zinc layer under the action of gravity.

[0030] like Figure 6 The lifting assembly 4 shown includes a bracket 41 and a third roller 42. The bracket 41 is provided on one side of the galvanizing tank 1. The third roller 42 is rotatably connected inside the bracket 41. The lower surface of the strip steel 5 is rolled around the outer side of the third roller 42. The bracket 41 is rotatably connected to two parallel fourth roller shafts 43. The two fourth roller shafts 43 are arranged longitudinally, and the strip steel 5 is rolled around the periphery of the two fourth roller shafts 43. One of the fourth roller shafts 43 is connected to the output end of the drive unit 44, and the fixed end of the drive unit 44 is installed on the outside of the bracket 41.

[0031] like Figure 6 As shown, a pressure roller 45 is also rotatably connected inside the bracket 41. The pressure roller 45 is located above the uppermost fourth roller shaft 43. The outer periphery of the pressure roller 45 is rolled to the upper surface of the strip steel 5. The pressure roller 45 is used to press on the upper surface of the strip steel 5 to ensure that the strip steel 5 can smoothly wrap around the fourth roller shaft 43.

[0032] like Figure 7As shown, the drive unit 44 includes a servo motor 441, a synchronous belt 442, and a synchronous pulley 443. The servo motor 441 is mounted on the lower end of the bracket 41. The output pulley of the servo motor 441 and the synchronous pulley 443 are sleeved with the synchronous belt 442 to form a synchronous transmission structure. The synchronous pulley 443 is fixedly sleeved on one end of any of the fourth roller shafts 43. The servo motor 441 is existing technology, and its model is K8LS50N2. When the strip steel 5 enters the lifting assembly 4 through the flat surface, the strip steel 5 passes through the periphery of the two fourth roller shafts 43 in a winding manner. The controller controls the servo motor 41 to start, and the servo motor 441 drives the synchronous pulley 443 through the synchronous belt 442. Rotating roller 43 drives the fourth roller 43 connected to it to rotate. The friction between the roller and the strip surface generates traction force, which continuously pulls the strip 5 upward. A lifting component 4 is provided, which can pull the galvanized strip 5 to a higher position. During the traction process, the zinc layer can be cooled and the strip 5 can be straightened, which can accelerate the cooling speed of the zinc liquid and better connect with downstream processes. The vertical layout of the device reduces the floor space and improves the utilization rate of the plant space. The galvanized strip is wrapped between the fourth roller 43 to prevent the strip 5 from falling due to gravity during the lifting process. It can also flatten the zinc layer on the surface of the strip, reduce safety hazards, improve production efficiency, and increase the yield rate.

[0033] Working process of a continuous strip galvanizing device: The strip steel 5 enters the galvanizing bath 1 from the discharge end of the upstream process. Under the action of the galvanizing assembly 2, galvanizing is completed. In the galvanizing assembly, multiple staggered first rollers 21 and second rollers 22 guide the strip steel to form a wavy trajectory, prolonging the contact time with the zinc liquid and ensuring uniform surface immersion. The strip steel 5 is smoothly discharged from the galvanizing bath 1 by the drum-shaped guide rollers 23. The discharged strip steel enters the surface leveling assembly 3, first passing through two axially symmetrical scrapers 32, whose scraping ends abut against both sides of the strip steel to scrape off excess zinc layer and initially level it. Two sets of air knives 33 located above the scrapers then operate. A high-pressure air pump supplies air to the jet frame 331 through the air inlet pipe 333. Multiple nozzles 332 spray high-speed airflow onto the surface of the strip steel 5 to further refine and flatten the zinc layer. The strip steel 5, after surface treatment, enters the lifting assembly 4. It is first supported and guided from below by the third roller shaft 42, and then wrapped around two fourth roller shafts 43 arranged longitudinally inside the bracket 41. The servo motor 441 of the drive unit 44 drives the fourth roller shaft to rotate through the synchronous belt 442 and the synchronous pulley 443. The friction force is used to stably lift the strip steel, and it enters the next process under the action of the traction roller shaft of the downstream process.

[0034] The control method in this embodiment is controlled by a controller. The controller circuit can be implemented by simple programming by those skilled in the art. The power supply is also common knowledge in the art. Furthermore, this document is mainly used to protect mechanical devices, and the control method and circuit connection will not be explained in detail here.

[0035] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A continuous strip galvanizing apparatus, comprising a galvanizing tank (1) disposed below a foundation, characterized in that: It also includes a galvanizing assembly (2), a surface leveling assembly (3), and a lifting assembly (4). The galvanizing assembly (2) is installed in the galvanizing tank (1). One end of the galvanizing tank (1) is connected to the discharge end of the upstream process. The other end of the galvanizing tank (1) is connected to the surface leveling assembly (3) and the lifting assembly (4) in sequence along the traveling direction of the strip (5). The galvanizing assembly (2) is used to uniformly galvanize the surface of the strip (5). The surface leveling assembly (3) is used to level the zinc layer on the surface of the strip (5). The lifting assembly (4) is used to lift the galvanized strip (5).

2. The continuous strip galvanizing apparatus according to claim 1, characterized in that: The galvanizing assembly (2) includes a first roller (21) and a second roller (22). Multiple first rollers (21) and multiple second rollers (22) are arranged in sequence in the galvanizing bath (1) along the traveling direction of the strip (5). The outer periphery of the first roller (21) is rolled to the upper surface of the strip (5), and the outer periphery of the second roller (22) is rolled to the lower surface of the strip (5). The first rollers (21) and the second rollers (22) are arranged alternately in the galvanizing bath (1).

3. The continuous strip galvanizing apparatus according to claim 2, characterized in that: The galvanizing assembly (2) also includes a guide roller shaft (23), which is rotatably installed inside the galvanizing bath (1). The guide roller shaft (23) is a drum-shaped roller and is used to guide the strip steel (5) out of the galvanizing bath (1).

4. The continuous strip galvanizing apparatus according to claim 1, characterized in that: The surface smoothing component (3) includes a frame (31), two scrapers (32) and two sets of air knives (33). The frame (31) is set at the upper end of the galvanizing tank (1). Two scrapers (32) are set inside the frame (31). The two scrapers (32) are located on both sides of the strip steel (5) respectively. The two scrapers (32) are set opposite to each other. The scraping end of each scraper (32) abuts against one side of the strip steel (5). A set of air knives (33) is set above each scraper (32).

5. The continuous strip galvanizing apparatus according to claim 4, characterized in that: The air knife (33) includes an air jet frame (331), a nozzle (332) and an air inlet pipe (333). Multiple air jet frames (331) are installed on the frame (31). Multiple nozzles (332) are installed in each air jet frame (331). The air jet end of the nozzle (332) faces the strip (5). The air inlet end of the nozzle (332) is connected to one end of the air inlet pipe (333). The air inlet pipe (333) is installed in the frame and the other end of the air inlet pipe (333) is connected to an external high-pressure air pump.

6. The continuous strip galvanizing apparatus according to claim 1, characterized in that: The lifting assembly (4) includes a bracket (41) and a third roller (42). The bracket (41) is provided on one side of the galvanizing tank (1). The third roller (42) is rotatably connected inside the bracket (41). The lower surface of the strip (5) is rolled around the outer side of the third roller (42). The bracket (41) is rotatably connected to two parallel fourth roller shafts (43). The two fourth roller shafts (43) are arranged longitudinally, and the strip steel (5) is rolled around the periphery of the two fourth roller shafts (43). One of the fourth roller shafts (43) is connected to the output end of the drive unit (44), and the fixed end of the drive unit (44) is installed on the outside of the bracket (41).

7. A continuous strip galvanizing apparatus according to claim 6, characterized in that: The support (41) also rotatably connects to the pressure roller (45), which is located above the fourth roller shaft (43) at the top. The outer periphery of the pressure roller (45) is rolled to the upper surface of the strip (5).

8. The continuous strip galvanizing apparatus according to claim 7, characterized in that: The drive unit (44) includes a servo motor (441), a synchronous belt (442), and a synchronous pulley (443). The servo motor (441) is mounted on the lower end of the bracket (41). The output wheel of the servo motor (441) and the synchronous pulley (443) are sleeved with the synchronous belt (442) to form a synchronous transmission structure. The synchronous pulley (443) is fixedly sleeved on one end of any fourth roller shaft (43).

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