Three-stage synchronous belt transmission mechanism

Abstract

The invention relates to the technical field of transmission mechanisms, in particular to a three-stage synchronous belt transmission mechanism which is characterized in that a tensioning part is located at the end of a three-stage belt wheel set and fixedly connected with a third-stage pallet fork, and when a third synchronous belt extends, the tensioning part is tensioned and pulls the third synchronous belt outwards; through mutual cooperation of the first-stage belt wheel set, the second-stage belt wheel set and the third-stage belt wheel set, goods are loaded and unloaded stably, the synchronous belt is high in precision, small in tooth space error, high in transmission efficiency, small in noise and long in service life, the defects of a traditional transmission mode in the aspects of positioning precision and transmission stability are successfully overcome, meanwhile, the stroke range of the mechanism is effectively expanded, and the transmission efficiency is improved. A new solution is provided for the development of the intelligent warehousing system; and the tensioning part compensates the elongation of the third synchronous belt caused by long-time use, so that the influence on the cargo loading and unloading stability of the top connecting plate due to the elongation of the third synchronous belt is avoided, and the transmission mechanism can load and unload cargoes stably.

Description

Technical Field

[0001] The present invention relates to the technical field of transmission mechanisms, in particular to a three-stage synchronous belt transmission mechanism. Background Art

[0002] With the continuous progress of society, intelligent manufacturing has become a general consensus to promote development. Under this trend, stereoscopic warehouses and intelligent storage systems have sprung up, and equipment such as forks and robotic arms with multi-level synchronous transmission technology have also emerged to meet the growing demand. Multi-level synchronous transmission, also known as multi-axis system synchronous control, refers to the process of maintaining a certain synchronous operation relationship between the axes in most multi-axis transmission system applications. The multi-axis system is a nonlinear, strongly coupled multi-input and multi-output system. The main performance indicators of multi-axis synchronous control are: speed proportional synchronization, position (or angle) synchronization, and absolute value error less than a certain limit value. Multi-axis synchronous control is an interdisciplinary comprehensive technology. It is an organic combination of power electronics technology, electrical transmission technology, information technology, control technology and mechanical technology. Its development is closely linked to the development of other related technologies. The so-called synchronous control means that a coordinate motion instruction can drive two motors to run simultaneously. By detecting the movement of the two motors, the displacement deviation is fed back to the CNC system to obtain synchronous error compensation. The purpose is to control the displacement deviation between the master and slave motors within an allowable range.

[0003] In high-bay warehouses and intelligent storage systems, equipment such as multi-level forks and robotic arms play a core role. They are key transfer tools for storing and retrieving items. At present, most of these devices on the market use chain and gear transmission. However, this traditional transmission method has problems such as limited travel and insufficient stability of the transmission process, and the high cost limits its popularity in large-scale applications. Summary of the invention

[0004] The main purpose of the present invention is to provide a three-stage synchronous belt transmission mechanism to solve the problems of limited travel, insufficient stability of the transmission process and high cost proposed in the related art.

[0005] In order to achieve the above object, according to one aspect of the present invention, there is provided a three-stage synchronous belt transmission mechanism, which is fixedly mounted on a three-stage telescopic fork, comprising: a primary pulley group, the primary pulley group is fixedly mounted on a first-stage fork, the primary pulley group comprises a first drive group and a first transmission group, the first drive group is used to drive the first transmission group to rotate; A secondary pulley group, the secondary pulley group is fixedly mounted on the second-stage fork, the secondary pulley group comprises a transition group, a second drive group, a second transmission group and a connecting portion, the first transmission group drives the second drive group to rotate through the transition group, the second drive group is used to drive the second transmission group to rotate, and the connecting portion is provided on the second transmission group; A three-stage pulley group, which is fixedly mounted on the third-stage fork, and includes a support group, a loading and unloading group, and a third synchronous belt. The second transmission group drives the three-stage pulley group to extend forward or pull back and shorten through the connecting part; The tensioning part is located at the end of the third-stage pulley group and is fixedly connected to the third-stage fork. When the third synchronous belt is extended, the tensioning part is tensioned to pull the third synchronous belt outward.

[0006] Furthermore, the first drive group includes a power source, a first transmission shaft and a first pulley, the power source is fixedly mounted on the first-stage fork, one end of the first transmission shaft is fixedly connected to the power source, and the other end is rotatably connected to the first-stage fork, the first pulley is fixedly sleeved on the first transmission shaft, and the power source drives the first pulley to rotate via the first transmission shaft.

[0007] Furthermore, the first transmission group includes a first synchronous belt, a second transmission shaft and a second pulley, both ends of the second transmission shaft are fixedly connected to the first-stage fork, the second pulley is rotatably sleeved on the outer ring of the second transmission shaft, the first synchronous belt is sleeved on the outer rings of the first pulley and the second pulley, and the first pulley drives the first synchronous belt and the second pulley to rotate.

[0008] Furthermore, the transition group includes a transition wheel, a first fixed wheel and a second fixed wheel, and the transition wheel, the first fixed wheel and the second fixed wheel are all rotatably arranged on the second-level fork, and the upper section of the first synchronous belt passes through the lower surface of the second fixed wheel, the upper surface of the transition wheel and the lower surface of the first fixed wheel in sequence, and drives the transition wheel to rotate.

[0009] Furthermore, the second drive group includes a fourth transmission shaft, a third transmission shaft and a third pulley, one end of the third transmission shaft is fixedly connected to the transition wheel, and the other end is rotatably connected to the second-stage fork, both ends of the fourth transmission shaft are fixedly connected to the second-stage fork, and the third pulley is fixedly sleeved on the outer ring of the third transmission shaft.

[0010] Furthermore, the second transmission group includes a second synchronous belt, a toothed connecting plate and a fourth pulley, the fourth pulley is rotatably sleeved on the outer ring of the fourth transmission shaft, the second synchronous belt is sleeved on the outer rings of the third pulley and the fourth pulley, the third pulley drives the second synchronous belt to rotate between the third pulley and the fourth pulley, the toothed connecting plate is fixedly arranged on the upper section of the second synchronous belt and moves between the third pulley and the fourth pulley, and an overpressure groove is provided inside the toothed connecting plate.

[0011] Furthermore, the connecting portion includes a first armature block, a second armature block, a first deep groove ball bearing and a second deep groove ball bearing, the first armature block is fixedly connected to the toothed connecting plate, the second armature block is fixedly connected to the third-level fork, the first deep groove ball bearing is fixedly arranged on the first armature block, and the second deep groove ball bearing is fixedly arranged on the second armature block.

[0012] Furthermore, the support group includes a fifth transmission shaft, a fifth pulley, a sixth transmission shaft and a sixth pulley, one end of the fifth transmission shaft is fixedly connected to the first deep groove ball bearing, and the other end is fixedly connected to the second deep groove ball bearing, the fifth pulley is fixedly sleeved on the outer ring of the fifth transmission shaft, both ends of the sixth transmission shaft are fixedly connected to the third-stage fork, the sixth pulley is rotatably sleeved on the outer ring of the sixth transmission shaft, the loading and unloading group includes a third synchronous belt and a top connecting plate, the third synchronous belt is sleeved on the outer rings of the fifth pulley and the sixth pulley, and the top connecting plate is fixedly mounted on the third synchronous belt for loading and unloading goods.

[0013] Further, the tensioning part includes an adjustment group, a connection group and a tensioning group, the adjustment group includes a knob, a first guide rod and a second guide rod, the connection group includes a fixed plate, a top plate, a bottom plate and a plurality of connecting rings, the fixed plate is fixedly connected to the third-stage fork, the knob is threadedly connected to the fixed plate, the first guide rod and the second guide rod are both slidably connected to the fixed plate, the bottom ends of the knob, the first guide rod and the second guide rod are fixedly connected to the top plate, the outer ring of the connecting ring is fixedly connected to the bottom plate, and the connecting ring is rotatably sleeved on the outer ring of the sixth transmission shaft.

[0014] Further, the tensioning group includes a plurality of springs and a plurality of clamping parts, the clamping parts are fixedly arranged on the inner side of the top plate and the inner side of the bottom plate, the springs are arranged between two opposite clamping parts, the clamping parts include a snap ring group and a support rod group, the snap ring group includes a snap ring body and a snap ring buckle, the snap ring buckle is fixedly arranged on the top of the snap ring body, the snap ring buckle end is buckled inward, and the bottom end of the snap ring body is fixedly arranged on the inner surface of the top plate or the bottom plate, the support rod group includes a first support rod, a first hook, a second support rod and a second hook, the bottom ends of the first support rod and the second support rod are fixedly connected to the snap ring body, the first hook is fixedly arranged on the top of the first support rod, the second hook is fixedly arranged on the top of the second support rod, and the first hook and the second hook are bent towards each other.

[0015] Compared with the prior art, the present invention has the following beneficial effects: the second synchronous belt drives the connecting part to slide back and forth between the third pulley and the fourth pulley through the toothed connecting plate, so that the three-stage pulley group is pushed forward to extend or pulled back to shorten; the first-stage pulley group is fixed on the first-stage fork to provide power for the second-stage pulley group; the second-stage pulley group is fixed on the second-stage fork to extend or shorten with the second-stage fork and provide power for the third-stage pulley group; the third-stage pulley group is fixed on the third-stage fork to extend or shorten with the third-stage fork, so that the goods are loaded on the top connecting plate or from the top connecting plate The third synchronous belt can be slightly stretched after a long period of use. At this time, the spring rebounds to pull the sixth transmission shaft outwards and tighten the third synchronous belt to avoid affecting the stability of loading and unloading goods on the top connecting plate due to the elongation of the third synchronous belt. When the spring rebound cannot make up for the elongation of the third synchronous belt, turn the knob, move outwards along the fixed plate, and pull the top plate toward the fixed plate, so that the spring stretches and the sixth transmission shaft is pulled outwards until the elongation of the third synchronous belt is completely compensated, thereby ensuring that the transmission mechanism can load and unload goods smoothly. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is an overall schematic diagram of the present invention; Figure 2 A top view of the present invention; Figure 3 It is a side view of the present invention; Figure 4 It is a schematic diagram of the tensioning part structure of the present invention; Figure 5 This is a schematic diagram of the structure of the clamping part of the present invention; Figure 6 It is a schematic diagram of the structure of the connecting part of the present invention; Figure 7 This is a diagram of the contraction state of the present invention.

[0017] Illustration Description: 1. Primary pulley group; 11. Power source; 12. First transmission shaft; 13. First pulley; 14. First synchronous belt; 15. Second transmission shaft; 16. Second pulley; 2. Secondary pulley assembly; 20. Fourth transmission shaft; 21. Third transmission shaft; 22. Third pulley; 23. Transition wheel; 24. First fixed wheel; 25. Second fixed wheel; 26. Second synchronous belt; 27. Toothed connecting plate; 28. Connecting part; 29. ​​Fourth pulley; 271. Overpressure groove; 281. First armature block; 282. Second armature block; 283. First deep groove ball bearing; 284. Second deep groove ball bearing; 3. Three-stage pulley group; 31. Fifth transmission shaft; 32. Fifth pulley; 33. Third synchronous belt; 34. Top connecting plate; 35. Sixth transmission shaft; 36. Sixth pulley; 4. Tensioning portion; 41. Fixing plate; 42. Top plate; 43. Bottom plate; 44. Spring; 45. Clamping portion; 46. Knob; 47. First guide rod; 48. Second guide rod; 49. Connecting ring; 451. Clamping ring body; 452. Clamping ring buckle; 453. First support rod; 454. First hook; 455. Second support rod; 456. Second hook. DETAILED DESCRIPTION

[0018] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the specific implementation mode, structure, characteristics and effects of the present invention are described in detail below in combination with the accompanying drawings and preferred embodiments.

[0019] See also Figures 1 to 7 , This embodiment provides a three-stage synchronous belt transmission mechanism, which is fixedly mounted on a three-stage telescopic fork, including: a primary pulley group 1, which is fixedly mounted on a first-stage fork, and the primary pulley group 1 includes a first drive group and a first transmission group, and the first drive group is used to drive the first transmission group to rotate; The secondary pulley group 2 is fixedly mounted on the second-stage fork. The secondary pulley group 2 includes a transition group, a second drive group, a second transmission group and a connecting portion 28. The first transmission group drives the second drive group to rotate through the transition group. The second drive group is used to drive the second transmission group to rotate. The connecting portion 28 is provided on the second transmission group. The third-level pulley group 3 is fixedly installed on the third-level fork. The third-level pulley group 3 includes a support group, a loading and unloading group and a third synchronous belt 33. The second transmission group drives the third-level pulley group 3 to extend forward or pull back and shorten through the connecting part 28; The tensioning part 4 is located at the end of the third-stage pulley group 3 and is fixedly connected to the third-stage fork. When the third synchronous belt 33 is extended, the tensioning part 4 is tightened to pull the third synchronous belt 33 outward.

[0020] The first drive group includes a power source 11, a first transmission shaft 12 and a first pulley 13. In this embodiment, a motor is preferably used as the power source 11 to drive the first transmission shaft 12 to rotate. The power source 11 is fixedly arranged on the first-stage fork. One end of the first transmission shaft 12 is fixedly connected to the power source 11, and the other end is rotationally connected to the first-stage fork. The first pulley 13 is fixedly sleeved on the first transmission shaft 12. The power source 11 drives the first pulley 13 to rotate through the first transmission shaft 12.

[0021] The first transmission group includes a first synchronous belt 14, a second transmission shaft 15 and a second pulley 16. Both ends of the second transmission shaft 15 are fixedly connected to the first-stage fork. The second pulley 16 is rotatably sleeved on the outer ring of the second transmission shaft 15. The first synchronous belt 14 is sleeved on the outer rings of the first pulley 13 and the second pulley 16. The first pulley 13 drives the first synchronous belt 14 and the second pulley 16 to rotate.

[0022] The transition group includes a transition wheel 23, a first fixed wheel 24 and a second fixed wheel 25. The transition wheel 23, the first fixed wheel 24 and the second fixed wheel 25 are all rotatably arranged on the second-stage fork. The upper section of the first synchronous belt 14 passes through the lower surface of the second fixed wheel 25, the upper surface of the transition wheel 23 and the lower surface of the first fixed wheel 24 in sequence, and drives the transition wheel 23 to rotate. The first fixed wheel 24 and the second fixed wheel 25 make the first synchronous belt 14 form a wrap angle of 120° on the transition wheel 23 for easy transmission.

[0023] The second drive group includes a fourth transmission shaft 20, a third transmission shaft 21 and a third pulley 22. One end of the third transmission shaft 21 is fixedly connected to the transition wheel 23, and the other end is rotatably connected to the second-stage fork. Both ends of the fourth transmission shaft 20 are fixedly connected to the second-stage fork, and the third pulley 22 is fixedly sleeved on the outer ring of the third transmission shaft 21.

[0024] The second transmission group includes a second synchronous belt 26, a toothed connecting plate 27 and a fourth pulley 29. The fourth pulley 29 is rotatably sleeved on the outer ring of the fourth transmission shaft 20. The second synchronous belt 26 is sleeved on the outer rings of the third pulley 22 and the fourth pulley 29. The third pulley 22 drives the second synchronous belt 26 to rotate between the third pulley 22 and the fourth pulley 29. The toothed connecting plate 27 is fixedly arranged on the upper section of the second synchronous belt 26 and moves between the third pulley 22 and the fourth pulley 29. An overpressure groove 271 is provided inside the toothed connecting plate 27 to prevent the toothed connecting plate 27 from excessively squeezing the second synchronous belt 26 and causing damage to the second synchronous belt 26.

[0025] The connecting portion 28 includes a first armature block 281, a second armature block 282, a first deep groove ball bearing 283 and a second deep groove ball bearing 284. The first armature block 281 is fixedly connected to the toothed connecting plate 27, the second armature block 282 is fixedly connected to the third-stage fork, the first deep groove ball bearing 283 is fixedly arranged on the first armature block 281, and the second deep groove ball bearing 284 is fixedly arranged on the second armature block 282.

[0026] The support group includes a fifth transmission shaft 31, a fifth pulley 32, a sixth transmission shaft 35 and a sixth pulley 36. One end of the fifth transmission shaft 31 is fixedly connected to the first deep groove ball bearing 283, and the other end is fixedly connected to the second deep groove ball bearing 284. The fifth pulley 32 is fixedly sleeved on the outer ring of the fifth transmission shaft 31. Both ends of the sixth transmission shaft 35 are fixedly connected to the third-stage fork. The sixth pulley 36 is rotatably sleeved on the outer ring of the sixth transmission shaft 35. The loading and unloading group includes a third synchronous belt 33 and a top connecting plate 34. The third synchronous belt 33 is sleeved on the outer rings of the fifth pulley 32 and the sixth pulley 36. The top connecting plate 34 is fixedly mounted on the third synchronous belt 33 for loading and unloading goods.

[0027] The tensioning part 4 includes an adjustment group, a connection group and a tensioning group. The adjustment group includes a knob 46, a first guide rod 47 and a second guide rod 48. The connection group includes a fixed plate 41, a top plate 42, a bottom plate 43 and a plurality of connecting rings 49. The fixed plate 41 is fixedly connected to the third-stage fork. The knob 46 is threadedly connected to the fixed plate 41. When the knob 46 is screwed out, the top plate 42 is pulled outward, the spring 44 is tensioned, and the third synchronous belt 33 is pulled outward at the same time, so that the third synchronous belt 33 maintains a certain tension to ensure smooth loading and unloading of goods. The first guide rod 47 and the second guide rod 48 are both slidably connected to the fixed plate 41. The bottom ends of the knob 46, the first guide rod 47 and the second guide rod 48 are fixedly connected to the top plate 42. The outer ring of the connecting ring 49 is fixedly connected to the bottom plate 43. The connecting ring 49 is rotatably sleeved on the outer ring of the sixth transmission shaft 35.

[0028] The tensioning group includes a plurality of springs 44 and a plurality of clamping parts 45. The clamping parts 45 are fixedly arranged on the inner side of the top plate 42 and the inner side of the bottom plate 43. The springs 44 are arranged between two opposite clamping parts 45. The clamping part 45 includes a clamping ring group and a support rod group. The clamping ring group includes a clamping ring body 451 and a clamping ring buckle 452. The clamping ring buckle 452 is fixedly arranged on the top of the clamping ring body 451. The end of the clamping ring buckle 452 is buckled inward to prevent the end of the spring 44 from slipping out of the clamping part 45, causing the tensioning part 4 to lose its tensioning effect. The bottom end of the clamping ring body 451 is fixedly arranged on the top On the inner surface of the plate 42 or the bottom plate 43, the support rod group includes a first support rod 453, a first hook 454, a second support rod 455 and a second hook 456. The bottom ends of the first support rod 453 and the second support rod 455 are fixedly connected to the clamping ring body 451. The first hook 454 is fixedly arranged on the top of the first support rod 453, and the second hook 456 is fixedly arranged on the top of the second support rod 455. The first hook 454 and the second hook 456 are bent towards each other to prevent the end of the spring 44 from slipping out of the clamping portion 45, causing the tensioning portion 4 to lose its tensioning effect.

[0029] In this embodiment, the transmission mechanism is preferably installed on a three-stage telescopic fork as an example.

[0030] Start the power source 11, the power source 11 drives the first pulley 13 to rotate through the first transmission shaft 12, the first pulley 13 drives the first synchronous belt 14 to rotate around the first pulley 13 and the second pulley 16, the rotating first synchronous belt 14 drives the transition wheel 23 to rotate, the transition wheel 23 drives the third pulley 22 to rotate through the third transmission shaft 21, the third pulley 22 drives the second synchronous belt 26 to reciprocate between the third pulley 22 and the fourth pulley 29, the rotating second synchronous belt 26 drives the connecting part 28 to slide back and forth between the third pulley 22 and the fourth pulley 29 through the toothed connecting plate 27, the three-stage pulley group 3 is pushed forward to extend or pulled back to shorten, the first-stage pulley group 1 is fixed on the first-stage fork, and provides power for the second-stage pulley group 2, the second-stage pulley group 2 is fixed on the second-stage fork, extends or shortens with the second-stage fork, and provides power for the three-stage belt The wheel group 3 provides power, and the three-stage pulley group 3 is fixed on the third-stage fork, and extends or shortens with the third-stage fork, so that the goods are loaded on the top connecting plate 34 or unloaded from the top connecting plate 34, thereby realizing the loading and unloading of goods; after a long period of use, the third synchronous belt 33 will undergo a slight elongation. At this time, the spring 44 rebounds, pulling the sixth transmission shaft 35 outward, and tightening the third synchronous belt 33 to avoid affecting the stability of loading and unloading goods on the top connecting plate 34 due to the elongation of the third synchronous belt 33. When the rebound amount of the spring 44 cannot make up for the elongation of the third synchronous belt 33, the knob 46 is turned, and the knob 46 moves outward along the fixed plate 41 to pull the top plate 42 toward the fixed plate 41, so that the spring 44 stretches and at the same time pulls the sixth transmission shaft 35 outward until the elongation of the third synchronous belt 33 is completely compensated, thereby ensuring that the transmission mechanism can load and unload goods smoothly.

[0031] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technical personnel in this field can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A three-stage synchronous belt transmission mechanism, fixedly mounted on a three-stage telescopic fork, characterized in that: include: A first-stage pulley assembly (1), the first-stage pulley assembly (1) is fixedly mounted on the first-stage fork, the first-stage pulley assembly (1) comprises a first drive assembly and a first transmission assembly, the first drive assembly is used to drive the first transmission assembly to rotate; A secondary pulley group (2), the secondary pulley group (2) is fixedly mounted on the second-stage fork, the secondary pulley group (2) comprises a transition group, a second drive group, a second transmission group and a connecting portion (28), the first transmission group drives the second drive group to rotate via the transition group, the second drive group is used to drive the second transmission group to rotate, and the connecting portion (28) is arranged on the second transmission group; A three-stage pulley group (3), the three-stage pulley group (3) is fixedly mounted on a third-stage cargo fork, the three-stage pulley group (3) comprises a support group, a loading and unloading group and a third synchronous belt (33), and the second transmission group drives the three-stage pulley group (3) to extend forward or to be pulled back and shortened via a connecting portion (28); A tensioning portion (4), the tensioning portion (4) being located at the end of the third-stage pulley group (3) and being fixedly connected to the third-stage fork; when the third synchronous belt (33) is extended, the tensioning portion (4) is tensioned to pull the third synchronous belt (33) outward.

2. The three-stage synchronous belt transmission mechanism according to claim 1, characterized in that: The first drive group comprises a power source (11), a first transmission shaft (12) and a first pulley (13); the power source (11) is fixedly mounted on the first-stage fork; one end of the first transmission shaft (12) is fixedly connected to the power source (11) and the other end is rotatably connected to the first-stage fork; the first pulley (13) is fixedly sleeved on the first transmission shaft (12); the power source (11) drives the first pulley (13) to rotate via the first transmission shaft (12).

3. The three-stage synchronous belt transmission mechanism according to claim 2, characterized in that: The first transmission group comprises a first synchronous belt (14), a second transmission shaft (15) and a second pulley (16); both ends of the second transmission shaft (15) are fixedly connected to the first-stage fork; the second pulley (16) is rotatably sleeved on the outer ring of the second transmission shaft (15); the first synchronous belt (14) is sleeved on the outer rings of the first pulley (13) and the second pulley (16); the first pulley (13) drives the first synchronous belt (14) and the second pulley (16) to rotate.

4. The three-stage synchronous belt transmission mechanism according to claim 3, characterized in that: The transition group comprises a transition wheel (23), a first fixed wheel (24) and a second fixed wheel (25); the transition wheel (23), the first fixed wheel (24) and the second fixed wheel (25) are all rotatably arranged on the second-stage fork; the upper section of the first synchronous belt (14) sequentially passes through the lower surface of the second fixed wheel (25), the upper surface of the transition wheel (23) and the lower surface of the first fixed wheel (24), and drives the transition wheel (23) to rotate.

5. The three-stage synchronous belt transmission mechanism according to claim 4, characterized in that: The second drive group comprises a fourth transmission shaft (20), a third transmission shaft (21) and a third pulley (22); one end of the third transmission shaft (21) is fixedly connected to the transition wheel (23), and the other end is rotatably connected to the second-stage fork; both ends of the fourth transmission shaft (20) are fixedly connected to the second-stage fork; and the third pulley (22) is fixedly sleeved on the outer ring of the third transmission shaft (21).

6. The three-stage synchronous belt transmission mechanism according to claim 5, characterized in that: The second transmission group comprises a second synchronous belt (26), a toothed connecting plate (27) and a fourth pulley (29); the fourth pulley (29) is rotatably sleeved on the outer ring of the fourth transmission shaft (20); the second synchronous belt (26) is sleeved on the outer rings of the third pulley (22) and the fourth pulley (29); the third pulley (22) drives the second synchronous belt (26) to rotate between the third pulley (22) and the fourth pulley (29); the toothed connecting plate (27) is fixedly arranged on the upper section of the second synchronous belt (26) and moves between the third pulley (22) and the fourth pulley (29); an overpressure groove (271) is provided inside the toothed connecting plate (27).

7. The three-stage synchronous belt transmission mechanism according to claim 6, characterized in that: The connecting portion (28) comprises a first chuck block (281), a second chuck block (282), a first deep groove ball bearing (283) and a second deep groove ball bearing (284); the first chuck block (281) is fixedly connected to the toothed connecting plate (27); the second chuck block (282) is fixedly connected to the third-stage fork; the first deep groove ball bearing (283) is fixedly arranged on the first chuck block (281); and the second deep groove ball bearing (284) is fixedly arranged on the second chuck block (282).

8. The three-stage synchronous belt transmission mechanism according to claim 7, characterized in that: The support group comprises a fifth transmission shaft (31), a fifth pulley (32), a sixth transmission shaft (35) and a sixth pulley (36); one end of the fifth transmission shaft (31) is fixedly connected to the first deep groove ball bearing (283), and the other end is fixedly connected to the second deep groove ball bearing (284); the fifth pulley (32) is fixedly sleeved on the outer ring of the fifth transmission shaft (31); both ends of the sixth transmission shaft (35) are fixedly connected to the third-stage cargo fork; the sixth pulley (36) is rotatably sleeved on the outer ring of the sixth transmission shaft (35); the loading and unloading group comprises a third synchronous belt (33) and a top connecting plate (34); the third synchronous belt (33) is sleeved on the outer rings of the fifth pulley (32) and the sixth pulley (36); the top connecting plate (34) is fixedly mounted on the third synchronous belt (33) for loading and unloading cargo.

9. The three-stage synchronous belt transmission mechanism according to claim 8, characterized in that: The tensioning portion (4) comprises an adjustment group, a connection group and a tensioning group. The adjustment group comprises a knob (46), a first guide rod (47) and a second guide rod (48). The connection group comprises a fixed plate (41), a top plate (42), a bottom plate (43) and a plurality of connection rings (49). The fixed plate (41) is fixedly connected to the third-stage fork. The knob (46) is threadedly connected to the fixed plate (41). The first guide rod (47) and the second guide rod (48) are both slidably connected to the fixed plate (41). The bottom ends of the knob (46), the first guide rod (47) and the second guide rod (48) are all fixedly connected to the top plate (42). The outer rings of the connection rings (49) are all fixedly connected to the bottom plate (43). The connection rings (49) are rotatably sleeved on the outer ring of the sixth transmission shaft (35).

10. The three-stage synchronous belt transmission mechanism according to claim 9, characterized in that: The tensioning group comprises a plurality of springs (44) and a plurality of clamping parts (45), the clamping parts (45) are fixedly arranged on the inner side of the top plate (42) and the inner side of the bottom plate (43), the springs (44) are arranged between two opposite clamping parts (45), the clamping parts (45) comprise a clamping ring group and a support rod group, the clamping ring group comprises a clamping ring body (451) and a clamping ring buckle (452), the clamping ring buckle (452) is fixedly arranged on the top of the clamping ring body (451), the end of the clamping ring buckle (452) is buckled inwardly, and the bottom of the clamping ring body (451) is fixedly arranged On the inner surface of the top plate (42) or the bottom plate (43), the support rod group comprises a first support rod (453), a first curved hook (454), a second support rod (455) and a second curved hook (456); the bottom ends of the first support rod (453) and the second support rod (455) are fixedly connected to the clamping ring body (451); the first curved hook (454) is fixedly arranged on the top of the first support rod (453); the second curved hook (456) is fixedly arranged on the top of the second support rod (455); and the first curved hook (454) and the second curved hook (456) are bent towards each other.

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