Dry grinding machine for ultrafine powder

Abstract

The utility model relates to the technical field of ultra-fine powder production, in particular to a dry type grinding machine for ultra-fine powder. Comprising a grinding machine body, and the grinding machine body comprises an assembling cylinder. According to the utility model, the slide bars and the cutter plates fixed on the slide bars are arranged in the feed hopper, so that the main shaft can drive the baffle plates to rotate and the rotating auger blades quantitatively convey materials into the grinding machine main body, and meanwhile, the main shaft drives the two slide bars to transversely reciprocate through the reciprocating assembly; a sliding rod located above the main shaft drives a cutter plate to cut up caked materials in the feeding hopper, after the cut-up materials make contact with rotating baffles, the baffles conduct quantitative material distribution on the materials, the baffles conduct secondary crushing on the caked materials in the material distribution process, and after the baffles convey the distributed materials to the position below the main shaft, the caked materials are conveyed to the position below the main shaft. The sliding rod located on the lower portion drives the cutter plate to crush cakes in the materials for three times, and the cakes are prevented from existing in the materials falling on the millstone.

Description

Technical Field

[0001] This utility model relates to the field of ultrafine powder production technology, specifically to a dry grinding machine for ultrafine powder. Background Technology

[0002] Vertical roller mills are typically used in the industrial production of ultrafine powders. These mills are used for grinding and screening ultrafine powders.

[0003] Existing vertical roller mills for ultrafine powders are typically equipped with a quantitative conveying mechanism. This mechanism is used to quantitatively convey granular materials into the mill. The materials entering the mill fall to the center of the grinding disc, which drives the materials inside to rotate at high speed. Under the action of centrifugal force, the materials reach the edge of the grinding disc, where they are crushed and pulverized by rollers located on the upper side of the edge of the grinding disc.

[0004] When the material conveyed by the quantitative conveying mechanism has a high moisture content, capillary bridging will form between the granular materials, causing the material to clump. Existing quantitative conveying mechanisms are usually composed of a rotary feeder and a screw conveyor, which has limited effect on crushing agglomerated materials. After the agglomerated material is conveyed to the middle position inside the grinding disc of the grinding mill by the quantitative conveying mechanism, the material agglomerates will be difficult to reach the edge position quickly under the action of centrifugal force due to their large weight, so that the rollers and grinding disc will cooperate to crush and grind them. This will cause the material to accumulate in the center of the grinding disc, reducing the grinding efficiency of the main body of the grinding mill. Utility Model Content

[0005] The purpose of this invention is to provide a dry grinding machine for ultrafine powders to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, this utility model aims to provide a dry grinding mill for ultrafine powders, comprising a grinding mill body, the grinding mill body including an assembly cylinder, a quantitative conveying mechanism provided on the outer side of the assembly cylinder, the quantitative conveying mechanism including a sealing cylinder fixed on the side wall of the assembly cylinder, a material equalization component provided on the upper side of one end of the sealing cylinder, the material equalization component including a feed hopper fixed on the sealing cylinder, a main shaft rotatably arranged inside the feed hopper, a feeding component provided on the main shaft, and slide rods rotatably arranged on both the upper and lower sides of the main shaft inside the feed hopper, two cutting plates symmetrically and rotatably fixed on the slide rods, with a gap between the other end of the cutting plate and the inner wall of the feed hopper, both ends of the slide rods slidingly penetrating through the side wall of the feed hopper and extending outwards, the end of the main shaft near the assembly cylinder rotatably penetrating one side of the feed hopper and provided with a reciprocating component, when the main shaft rotates, the reciprocating component drives the two slide rods to move synchronously and rotatably laterally, causing the cutting plates to cut the material inside the feed hopper.

[0007] As a further improvement to this technical solution, a positioning plate is fixed to the side of the feed hopper away from the assembly cylinder by a bracket. The end of the slide rod away from the assembly cylinder slides through the side wall of the positioning plate and extends outward. A convex ring is fixed on the slide rod at a position between the positioning plate and the feed hopper. A spring is provided between the convex ring and the positioning plate and sleeved on the slide rod. The spring pushes the convex ring away from the positioning plate.

[0008] As a further improvement to this technical solution, the reciprocating assembly includes a swashplate fixed on the main shaft. The end of the slide rod near the assembly cylinder slides in contact with the inclined surface of the swashplate. When the position where the slide rod contacts the swashplate is furthest from the feed hopper, the cutter plate contacts the side of the feed hopper inside that is close to the swashplate. When the position where the slide rod contacts the swashplate is closest to the feed hopper, the cutter plate contacts the side of the feed hopper inside that is far from the swashplate.

[0009] As a further improvement to this technical solution, the feeding assembly includes a number of baffles fixed in a ring array on the main shaft. The sidewalls of the baffles away from and near the swashplate, as well as the sidewalls of the baffles away from the main shaft, are in sliding contact with the inner wall of the feed hopper.

[0010] As a further improvement to this technical solution, the quantitative conveying mechanism also includes an auger shaft coaxially rotatably disposed inside the sealed cylinder. The auger shaft is fixed with auger blades that contact the inner circumference of the sealed cylinder. The end of the auger shaft away from the assembly cylinder rotatably passes through one side of the sealed cylinder and is fixed with a motor for driving the auger shaft to rotate. The motor is fixedly mounted on the sealed cylinder by a bracket.

[0011] As a further improvement to this technical solution, a drive wheel is coaxially fixed on the auger shaft at a position outside the sealing cylinder. The end of the main shaft away from the assembly cylinder rotates sequentially through one side of the feed hopper and the side wall of the positioning plate and is coaxially fixed with a driven wheel. The driven wheel and the drive wheel are connected by a transmission belt.

[0012] Compared with the prior art, the beneficial effects of this utility model are as follows:

[0013] 1. This dry grinding mill for ultrafine powders has a sliding rod and a cutter plate fixed on the sliding rod inside the feed hopper. The main shaft drives several baffles to rotate. The rotating auger blades quantitatively feed the material into the main body of the mill, while the main shaft drives two sliding rods to move laterally back and forth via a reciprocating assembly. The sliding rod above the main shaft drives the cutter plate to chop up the lumpy material inside the feed hopper. After the chopped material comes into contact with the rotating baffles, the baffles quantitatively distribute the material. During the distribution process, the baffles perform secondary crushing of the lumps in the material. After the baffles convey the distributed material to the area below the main shaft, the sliding rod below drives the cutter plate to perform a third crushing of the lumps in the material. This prevents lumps from remaining in the material falling onto the grinding disc, thus improving the grinding efficiency of the main body of the mill. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the overall structure of this utility model;

[0015] Figure 2 This is a cross-sectional view of the overall structure of this utility model;

[0016] Figure 3 This is a schematic diagram of the quantitative conveying mechanism of this utility model;

[0017] Figure 4 This is a cross-sectional view of the quantitative conveying mechanism of this utility model;

[0018] Figure 5 This is a schematic diagram of the material homogenization component of this utility model;

[0019] Figure 6 This is a cross-sectional view of the material equalization component of this utility model;

[0020] Figure 7 This is a partial structural diagram of the material homogenization component of this utility model.

[0021] The meanings of the labels in the diagram are as follows:

[0022] 1. Grinding machine body; 11. Assembly cylinder; 12. Central funnel; 13. Grinding disc; 14. Annular hollow frame; 16. Roller; 17. Air classifier;

[0023] 2. Quantitative conveying mechanism; 21. Sealed cylinder;

[0024] 22. Material distribution assembly; 221. Feed hopper; 222. Main shaft; 223. Driven wheel; 224. Drive belt; 225. Swashplate; 226. Positioning plate; 227. Baffle; 228. Slide rod; 2281. Convex ring; 2282. Spring; 229. Cutting blade;

[0025] 24. Motor; 25. Screw shaft; 251. Drive wheel; 26. Screw blade. Detailed Implementation

[0026] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0027] Example 1

[0028] Please see Figure 1 and Figure 2As shown, the purpose of this embodiment is to provide a dry grinding mill for ultrafine powders, including a grinding mill body 1. The grinding mill body 1 includes an assembly cylinder 11. A quantitative conveying mechanism 2 is provided on the outer side of the assembly cylinder 11. The quantitative conveying mechanism 2 is used to convey granular materials into the interior of the assembly cylinder 11. The quantitative conveying mechanism 2 includes a sealing cylinder 21 fixed to the side wall of the assembly cylinder 11. One end of the sealing cylinder 21 extends to the center position inside the assembly cylinder 11 and a central funnel 12 is fixed thereon. The central funnel 12 is fixed to the middle position of the middle section inside the assembly cylinder 11 by a bracket. The axis of the central funnel 12 and the axis of the assembly cylinder 11 are on the same straight line. The central funnel 12 is connected to the interior of the sealing cylinder 21. The quantitative conveying mechanism 2 is used to convey materials into the assembly cylinder 11. The material is fed into the central funnel 12, and then, guided by the central funnel 12, it falls into the grinding area of ​​the grinding mill body 1, where the grinding mill body 1 grinds the material into fine powder. The remaining structure of the grinding mill body 1 is described in detail below. A grinding disc 13 is installed inside the assembly cylinder 11 below the central funnel 12. A drive assembly for rotating the grinding disc 13 is installed on the lower side wall of the grinding disc 13. The drive assembly includes a drive motor and a reducer installed on the ground. The output shaft of the drive motor is coaxially and fixedly connected to the input shaft of the reducer. The output shaft of the reducer rotates through the lower side wall of the assembly cylinder 11 and is coaxially fixed to the lower side wall of the grinding disc 13. A ring-shaped contact is made with the circumferential side wall of the grinding disc 13, which is fixed to the inner wall of the assembly cylinder 11. The perforated frame 14 has several air slots arranged in a circular array on its surface. An air inlet pipe connected to the assembly cylinder 11 is fixed on one side of the assembly cylinder 11. The air inlet pipe is connected to the outlet pipe of an external blower, and the connection between the air inlet pipe and the assembly cylinder 11 is located on the lower side of the perforated frame 14. Several rollers 16 are arranged on the upper side wall of the grinding disc 13 near the edge. A wind classifier 17 is fixedly installed at the middle position of the top of the assembly cylinder 11. The wind classifier 17 is a mature product that can be easily purchased on the market, and its structure and working principle will not be described in detail here. When the quantitative conveying mechanism 2 conveys the material into the interior of the central funnel 12, the material falls through the central funnel 12 to the middle position of the upper side wall of the grinding disc 13. At this time, the drive component drives... The grinding disc 13 rotates at high speed, and the roller 16 rotates synchronously with it due to the friction between the roller 16 and the grinding disc 13. The grinding disc 13 drives the material on its upper side wall to rotate. Under the action of centrifugal force, the material on the grinding disc 13 moves to the gap between the roller 16 and the grinding disc 13, so that the roller 16 and the grinding disc 13 cooperate to crush the material into powder. At the same time, the blower blows air into the interior of the assembly cylinder 11, so that the airflow flows upward through several air slots. The high-speed airflow is then sucked into the operating air classifier 17. The material crushed into powder by the roller 16 and the grinding disc 13 moves to the top of the annular hollow frame 14 under the action of centrifugal force, and is then blown towards the air classifier 17 by the high-speed airflow. The fine powder in the material continues to be sucked into the air classifier 17 with the airflow.The air classifier 17 classifies the ingested powder. Powder that does not meet the predetermined particle size will fall from the coarse material outlet at the bottom of the air classifier 17 into the central funnel 12. Guided by the central funnel 12, it will fall again into the grinding disc 13 to mix with the new material and be ground again. Powder that meets the predetermined particle size will be discharged from the fine material outlet at the top of the air classifier 17 as a fine powder product, thus continuously producing standard-compliant fine powder products.

[0029] The remaining structure of the quantitative conveying mechanism 2 is described in detail below, referring to... Figure 3 and Figure 4 The quantitative conveying mechanism 2 also includes an auger shaft 25 coaxially rotatably disposed inside the sealed cylinder 21. Auger blades 26, which contact the inner circumferential wall of the sealed cylinder 21, are fixed on the auger shaft 25. One end of the auger shaft 25, away from the assembly cylinder 11, rotatably passes through one side of the sealed cylinder 21 and is fixed with a motor 24 for driving the auger shaft 25 to rotate. The motor 24 is fixedly mounted on the sealed cylinder 21 via a bracket. When the output shaft of the motor 24 drives the auger shaft 25 to rotate, the auger shaft 25 drives the auger blades 26 to rotate synchronously. Simultaneously, a material equalization assembly 22 is disposed on the upper side of one end of the sealed cylinder 21. The material equalization assembly 22 includes a feed hopper 221 fixed on the sealed cylinder 21. The upper end of the feed hopper 221 is connected to an external... The feeding pipe is connected, and the feeding hopper 221 is located above the auger blade 26. The feeding hopper 221 is connected to the inside of the sealing cylinder 21. A main shaft 222 is horizontally rotatably arranged inside the feeding hopper 221. A feeding component is arranged on the main shaft 222. When the main shaft 222 drives the feeding component to rotate, the feeding component feeds the material inside the feeding hopper 221 into the inside of the sealing cylinder 21 in a quantitative manner. When the feeding pipe transports the granular material into the inside of the feeding hopper 221, after the feeding component feeds the material into the inside of the sealing cylinder 21 in a quantitative manner, the rotating auger blade 26 transports the material towards the direction close to the central funnel 12, thereby quantitatively transporting the material into the inside of the grinding machine body 1 for grinding.

[0030] Meanwhile, a drive wheel 251 is coaxially fixed on the auger shaft 25 outside the sealing cylinder 21. The drive wheel 251 is located near the motor 24. The end of the main shaft 222 away from the assembly cylinder 11 rotates sequentially through one side of the feed hopper 221 and the side wall of the positioning plate 226, and a driven wheel 223 is coaxially fixed thereon. The driven wheel 223 and the drive wheel 251 are connected by a transmission belt 224. When the motor 24 drives the auger shaft 25 to rotate, the drive wheel 251 rotates synchronously with the auger shaft 25. The rotating drive wheel 251 drives the driven wheel 223 and the main shaft 222 to rotate synchronously through the transmission belt 224, causing the main shaft 222 to rotate and drive the feeding assembly to work. The structure of the feeding assembly is detailed below, refer to Figure 6The feeding assembly includes a ring array of baffles 227 fixed on the main shaft 222. The sidewalls of the baffles 227 away from and near the swashplate 225, as well as the sidewalls of the baffles 227 away from the main shaft 222, are in sliding contact with the inner wall of the feed hopper 221. That is, the remaining three sidewalls of the baffles 227 are in sliding contact with the sidewall of the sealing cylinder 21. A distribution cavity of the same size is formed between two adjacent baffles 227 and the circumferential sidewall of the main shaft 222. The distribution cavity rotates synchronously with the baffles 227. When a distribution chamber rotates to the top of the main shaft 222, the material inside the feed hopper 221 fills the distribution chamber under the action of gravity. Then the distribution chamber rotates to the bottom of the main shaft 222, and the material inside the distribution chamber falls into the interior of the sealing cylinder 21 under the action of gravity. Since each distribution chamber can be filled with the same amount of material, the feeding assembly can quantitatively deliver the material into the interior of the sealing cylinder 21, and then the auger blades 26 deliver it into the interior of the assembly cylinder 11 for grinding.

[0031] When the material entering the feed hopper 221 contains a lot of clumps due to high humidity, the clumps fall to the center of the grinding disc 13. Due to their weight, they are difficult to quickly reach the edge for crushing and grinding under centrifugal force, causing the material to accumulate in the center of the grinding disc 13 and reducing the grinding efficiency of the grinding machine body 1. To solve this problem, slide rods 228 are horizontally arranged inside the feed hopper 221 on both the upper and lower sides of the main shaft 222. Two cutter plates 229 are symmetrically fixed horizontally on the slide rods 228. The other end has a gap between itself and the inner wall of the feed hopper 221. Both ends of the slide rod 228 slide through the side wall of the feed hopper 221 and extend outward. The end of the main shaft 222 near the assembly cylinder 11 rotates through one side of the feed hopper 221 and is equipped with a reciprocating assembly. When the main shaft 222 rotates, the reciprocating assembly drives the two slide rods 228 to move laterally and reciprocally in sync. The slide rods 228 drive the cutter plate 229 to move synchronously, so that the cutter plate 229 cuts the material inside the feed hopper 221, thereby breaking up the agglomerated material and preventing agglomeration in the material falling onto the grinding disc 13.

[0032] Reference Figure 7 A positioning plate 226 is fixed to the side of the feed hopper 221 away from the assembly cylinder 11 by a bracket. The end of the slide rod 228 away from the assembly cylinder 11 slides through the side wall of the positioning plate 226 and extends outwards. A convex ring 2281 is fixed on the slide rod 228 at a position between the positioning plate 226 and the feed hopper 221. A spring 2282 is sleeved on the slide rod 228 between the convex ring 2281 and the positioning plate 226. The spring 2282 pushes the convex ring 2281 away from the positioning plate 226. The structure of the reciprocating assembly is detailed below, referring to... Figure 5The reciprocating assembly includes a swashplate 225 fixed to the main shaft 222. The swashplate 225 is inclined along the direction of the main shaft 222 and is positioned between the feed hopper 221 and the assembly cylinder 11. One end of the swashplate 225 is close to the sealing cylinder 21, and the other end is away from the sealing cylinder 21. The end of the slide rod 228 near the assembly cylinder 11 slides in contact with the inclined surface of the swashplate 225. When the main shaft 222 drives the swashplate 225 to rotate, relative sliding occurs between the swashplate 225 and the slide rod 228. When the position of the slide rod 228 in contact with the swashplate 225 moves closer to the swashplate 225 and closer to the feed hopper 221, the swashplate 225 pushes the slide rod 228 away from the assembly cylinder 11. The slide rod 228 drives the cutter plate 229 and the convex ring 2281 to move synchronously, reducing the distance between the convex ring 2281 and the positioning plate 226. At this time, the spring 2282 on the pushed slide rod 228 is compressed and contracted. When the position of the slide rod 228 in contact with the swashplate 225 moves closer to the swashplate 225 and closer to the feed hopper 221, the slide rod 228 moves further away from the assembly cylinder 11. When the swash plate 221 moves to its furthest position, the spring 2282 rebounds, pushing the convex ring 2281 and the slide rod 228 towards the swash plate 225. The slide rod 228 drives the cutter plate 229 and the convex ring 2281 to move synchronously, so that one end of the slide rod 228 remains in contact with the inclined surface of the swash plate 225, thereby realizing the lateral reciprocating movement of the slide rod 228. When the position where the slide rod 228 contacts the swash plate 225 is furthest from the feed hopper 221, the cutter plate 229 and the inside of the feed hopper 221 are closer to the swash plate 225. When the sliding rod 228 is closest to the feed hopper 221 at the point where it contacts the inclined plate 225, the cutter plate 229 contacts the side of the feed hopper 221 away from the inclined plate 225. In this way, during the transverse reciprocating movement of the sliding rod 228, the four cutter plates 229 can move on the cross-section of the feed hopper 221 to cut the material passing through the feed hopper 221, avoid the presence of lumps in the material falling on the grinding disc 13, and improve the grinding efficiency of the grinding machine body 1.

[0033] When this grinding machine is in use, the output shaft of the motor 24 drives the auger shaft 25, the drive wheel 251, and the auger blades 26 to rotate. Simultaneously, the drive wheel 251 drives the driven wheel 223 and the main shaft 222 to rotate via the transmission belt 224. The main shaft 222 drives several baffles 227 to rotate, and the main shaft 222 drives two sliding rods 228 to move synchronously laterally back and forth via a reciprocating assembly. When the feeding pipe conveys granular material into the feed hopper 221, the sliding rods 228 located above the main shaft 222 drive the corresponding cutter plates 229 to chop the agglomerated material. The chopped material then rotates... After contact with the baffle 227, several baffles 227 quantitatively distribute the material. During the distribution process, the baffles 227 perform secondary crushing of the lumps in the material. After the baffles 227 convey the distributed material to the bottom of the main shaft 222, the slide bar 228 located below drives the corresponding cutter plate 229 to crush the lumps in the material a third time. After the crushed material enters the interior of the sealed cylinder 21, the rotating auger blades 26 convey the material towards the direction close to the central funnel 12, thereby quantitatively conveying the material into the interior of the grinding machine body 1, so that the grinding machine body 1 grinds the material.

[0034] The foregoing has shown and described the basic principles, main features, and advantages of this utility model. Those skilled in the art should understand that this utility model is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the utility model. Various changes and modifications can be made to this utility model without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed utility model. The scope of protection of this utility model is defined by the appended claims and their equivalents.

Claims

1. A dry grinding mill for ultrafine powders, comprising a grinding mill body (1), the grinding mill body (1) including an assembly cylinder (11), and a quantitative conveying mechanism (2) provided on the outer side of the assembly cylinder (11), characterized in that: The quantitative conveying mechanism (2) includes a sealing cylinder (21) fixed on the side wall of the assembly cylinder (11). A material equalization component (22) is provided on the upper side of one end of the sealing cylinder (21). The material equalization component (22) includes a feeding hopper (221) fixed on the sealing cylinder (21). A main shaft (222) is laterally rotatably arranged inside the feeding hopper (221). A feeding component is provided on the main shaft (222). Slide rods (228) are laterally arranged inside the feeding hopper (221) at positions above and below the main shaft (222). Two cutting blades (229) are symmetrically fixed horizontally on the feed hopper (221). The other end of the cutting blade (229) is left with a gap between it and the inner wall of the feed hopper (221). Both ends of the sliding rod (228) slide through the side wall of the feed hopper (221) and extend outward. The end of the main shaft (222) near the assembly cylinder (11) rotates through one side of the feed hopper (221) and is equipped with a reciprocating assembly. When the main shaft (222) rotates, the reciprocating assembly drives the two sliding rods (228) to move horizontally and reciprocally in sync, so that the cutting blades (229) cut the material inside the feed hopper (221).

2. The dry grinding mill for ultrafine powders according to claim 1, characterized in that: A positioning plate (226) is fixed to the side of the feed hopper (221) away from the assembly cylinder (11) by a bracket. The end of the slide rod (228) away from the assembly cylinder (11) slides through the side wall of the positioning plate (226) and extends outward. A convex ring (2281) is fixed on the slide rod (228) at a position between the positioning plate (226) and the feed hopper (221). A spring (2282) is provided between the convex ring (2281) and the positioning plate (226) and is sleeved on the slide rod (228). The spring (2282) pushes the convex ring (2281) away from the positioning plate (226).

3. The dry grinding mill for ultrafine powders according to claim 1, characterized in that: The reciprocating assembly includes a swashplate (225) fixed on the main shaft (222). The end of the slide rod (228) near the assembly cylinder (11) slides in contact with the inclined surface of the swashplate (225). When the position of the slide rod (228) in contact with the swashplate (225) is farthest from the feed hopper (221), the cutter plate (229) contacts the side of the inside of the feed hopper (221) near the swashplate (225). When the position of the slide rod (228) in contact with the swashplate (225) is closest to the feed hopper (221), the cutter plate (229) contacts the side of the inside of the feed hopper (221) away from the swashplate (225).

4. The dry grinding mill for ultrafine powders according to claim 1, characterized in that: The feeding assembly includes a number of baffles (227) fixed in a ring array on the main shaft (222). The sidewalls of the baffles (227) away from and near the swashplate (225) and the sidewalls of the baffles (227) away from the main shaft (222) are in sliding contact with the inner wall of the feed hopper (221).

5. The dry grinding mill for ultrafine powders according to claim 1, characterized in that: The quantitative conveying mechanism (2) further includes an auger shaft (25) coaxially rotatably disposed inside the sealing cylinder (21). The auger shaft (25) is fixed with auger blades (26) that contact the inner circumference of the sealing cylinder (21). The end of the auger shaft (25) away from the assembly cylinder (11) rotatably passes through one side of the sealing cylinder (21) and is fixed with a motor (24) for driving the auger shaft (25) to rotate. The motor (24) is fixedly mounted on the sealing cylinder (21) by a bracket.

6. The dry grinding mill for ultrafine powders according to claim 5, characterized in that: The drive wheel (251) is coaxially fixed on the auger shaft (25) at a position outside the sealing cylinder (21). The end of the main shaft (222) away from the assembly cylinder (11) rotates sequentially through one side of the feed hopper (221) and the side wall of the positioning plate (226) and is coaxially fixed with a driven wheel (223). The driven wheel (223) and the drive wheel (251) are connected by a transmission belt (224).

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