A mechanical hand stacking device and stacking method

Abstract

The application relates to the technical field of stacking, in particular to a mechanical hand stacking device and a stacking method, which comprise a mechanical hand body, a fixing frame, a motor, a sliding assembly, a sliding frame, a vacuum suction cup and an adjusting assembly. The fixing frame is arranged on the mechanical hand body. A vacuum pump is arranged in the fixing frame, an adjusting cavity is formed in the fixing frame, and a motor is fixedly arranged in the adjusting cavity. A sliding assembly is arranged below the motor, the sliding assembly is connected with the sliding frame, vacuum suction cups are arranged on the fixing frame and the sliding frame, and the vacuum suction cups are divided into fixed suction cups and movable suction cups. The motor drives the sliding frame to slide through the sliding assembly. The adjusting assembly is arranged on the circumferential outer side of the sliding assembly, the movable suction cups are arranged on the adjusting assembly, and the sliding frame drives the movable suction cups to slide through the adjusting assembly. The position and the adsorption area of the vacuum suction cups are changed through sliding movement, the layout of the vacuum suction cups, the adsorption force and the size of goods are unified, the stacking quality is guaranteed, and the stacking efficiency is improved.

Description

Technical Field

[0001] This invention relates to the field of stacking technology, specifically to a robotic stacking device and stacking method. Background Technology

[0002] A stacking robot is an industrial device used for the automatic stacking and destacking of materials such as boxes, bags, cans, electrical appliances, sheets, tiles, and beer cartons. It is suitable for industries such as chemical, beverage, food, beer, and plastics.

[0003] The stacking robot for wooden doors mainly consists of a robot arm and an end effector. The end effector often adopts a vacuum adsorption mechanism, which uses a suction cup of the vacuum adsorption device to adhere to the surface of the wooden door. Then, a vacuum pump is used to create a vacuum and generate negative pressure, which makes the wooden door and the suction cup tightly bonded. Then, the multi-degree-of-freedom movement of the robot arm drives the wooden door to be placed in the designated position to complete the stacking.

[0004] However, the position of the suction cups in existing vacuum adsorption devices cannot be adjusted in real time. When the size of the wooden door changes, the suction cups need to be manually removed from the bracket and their positions adjusted so that the layout of the suction cups matches the size of the wooden door, resulting in low stacking efficiency.

[0005] In view of this, we propose a robotic stacking device and stacking method. Summary of the Invention

[0006] The purpose of this invention is to provide a robotic stacking device and stacking method to solve the problem of inconvenient adjustment of the vacuum suction cup layout mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A stacking method using a robotic arm includes the following steps: Step 1: Construct a model of the robotic stacking device and its working environment; We construct a kinematic model of the robotic stacking device and a working environment model of the robotic stacking device, thereby providing a foundation for subsequent path planning; Step 2: Set the initial and final position parameters and the moving step size of the robotic stacking device; Setting the initial position of the goods and the endpoint position to be stacked, and providing the distance that the robotic stacking device can move, provides a data basis for path planning; Step 3: Perform global path planning based on the RRT algorithm; The RRT algorithm is specifically a fast expanding random tree algorithm. It takes the initial coordinates of the goods as the starting point and the coordinates of the goods to be moved as the ending point. It constructs the node distance based on the movable step length of the robotic arm stacking device, and then randomly generates the movement path and performs obstacle avoidance planning for local optimization of the generated path. Step 4: The robotic stacking device stacks data based on a global path; The robotic stacking device obtains the optimized global path to stack the goods and complete the task.

[0008] Furthermore, step 3 also includes the following steps: Step 3.1: Use RRT to obtain the initial and final positions and movement step size for global path planning; Starting from the initial coordinates of the goods and ending at the coordinates where the goods need to be moved, the node distance is constructed using the movable step length of the robotic stacking device, and then the movement path is randomly generated. Step 3.2: Perform local path optimization based on the artificial potential field method; The artificial potential field method optimizes the randomly generated global path of the RRT algorithm, reduces redundant nodes, improves the movement efficiency of the robotic stacking device, and ensures stacking efficiency. Step 3.3: Import the final optimized path into the global path for replacement; The optimized path replaces the corresponding area in the global path, thereby generating an efficient and convenient global path.

[0009] Furthermore, step 3.2 also includes the following steps: Step 3.2.1: Determine if there are redundant nodes in the global path; The RRT algorithm performs random sampling based on a random strategy. As the algorithm progresses, the number of samplings increases, the number of branches and leaf nodes in the random tree increases, and the complexity of the random tree also increases. Therefore, redundant nodes may appear, and it is necessary to judge the redundant nodes. Step 3.2.2: If there are no redundant nodes, the data is transmitted to the robotic stacking device as the final path. If there are no redundant nodes, the path plan generated by the RRT algorithm is directly imported as a global path into the robotic stacking device for stacking goods. Step 3.2.3: If redundant nodes exist, import the start and end positions of the redundant nodes into the artificial potential algorithm. If redundant nodes exist, the road segment data of the redundant nodes are sent to the artificial potential algorithm, which then replans the path for that segment. Step 3.2.4: The artificial potential algorithm generates an optimized path based on the start and end positions of redundant nodes; The artificial potential algorithm optimizes the path based on the initial and final positions of redundant nodes and the step size of their movement.

[0010] Furthermore, step 3.3 also includes the following steps: Step 3.3.1: Determine if a collision has occurred in the current optimized path; The artificial potential algorithm is used to determine obstacle avoidance in the optimized path; Step 3.3.2: If no collision occurs, import the final optimized path into the global path for replacement. If there are no obstacles on the optimized path, the optimized path will be imported into the global path for replacement. Step 3.3.3: If a collision occurs, return to the artificial potential algorithm to regenerate the optimized path; If there are obstacles on the optimized path, the optimization result is returned to the artificial potential algorithm for replanning until there are no obstacles on the planned path trajectory, and then imported into the global path for replacement.

[0011] A robotic stacking device includes: a robotic arm body, a fixed frame, a motor, a sliding assembly, a sliding frame, vacuum suction cups, and an adjustment assembly. The fixed frame is fixedly mounted on the robotic arm body. A vacuum pump is installed inside the fixed frame, and an adjustment cavity is formed on the fixed frame. A motor is fixedly mounted inside the adjustment cavity, and the motor is located below the vacuum pump. A sliding assembly is located below the motor and is connected to the sliding frame. The sliding frame is slidably mounted on the fixed frame. Vacuum suction cups are installed on both the fixed frame and the sliding frame. The vacuum suction cups are connected to the vacuum pump via flexible hoses. The vacuum pump and each vacuum suction cup are connected via flexible hoses (not shown in the figure). The vacuum pump's suction causes the vacuum suction cups to generate suction force to pick up goods, thereby completing the stacking of goods. The vacuum suction cups are divided into fixed... The system includes a suction cup and a movable suction cup. When the size of the goods changes, the motor drives the sliding frame to slide and change the position of the fixed suction cup via a sliding component. After the size of the goods changes, the motor starts and drives the sliding frame to slide via the sliding component, which in turn drives the fixed suction cups fixedly connected to the sliding frame to move synchronously, thereby changing the position distribution of the vacuum suction cups, ensuring uniform force distribution, and ensuring the stability of stacking goods of different sizes. An adjustment component is provided on the outer circumference of the sliding component. The adjustment component is located on the fixed frame and has a movable suction cup. The sliding frame drives the movable suction cup to slide and adjust the suction force via the adjustment component. During the sliding process, the sliding frame drives the movable suction cup to slide and extend via the adjustment component, thereby making the movable suction cup contact the goods, increasing the suction area of ​​the vacuum suction cup, and thus ensuring the stability of the suction of the goods.

[0012] Preferably, the sliding frame includes front and rear frames and left and right frames; fixed suction cups are installed on the fixed frame, front and rear frames, and left and right frames; the front and rear frames are linearly arranged on the fixed frame, and the front and rear frames are slidably connected to the fixed frame; multiple left and right frames are linearly arranged on the front and rear frames, and the front and rear frames are slidably connected to the left and right frames; the front and rear frames slide symmetrically along the fixed frame, thereby driving the fixed suction cups fixedly installed on them to slide synchronously, completing the change of position in the front-rear direction to adapt to goods of different sizes; there are also two left and right frames, which are used to realize the position adjustment of the fixed suction cups in the left-right direction of the fixed frame, so as to adjust the position according to the size of the goods. The layout of the fixed suction cup is changed; the left and right frames include a fixed rod and a telescopic rod. The fixed rod is fixedly connected to the fixed frame, and the telescopic rods are slidably installed at both ends of the fixed rod. The telescopic rods are slidably connected to the front and rear frames; the telescopic rods are connected to the front and rear frames. When the front and rear frames slide horizontally, the front and rear frames will pull the telescopic rods to slide synchronously, thereby changing the overall length of the left and right rods, so that the positions of the left and right rods match those of the front and rear frames; the lower ends of the fixed frame and the front and rear frames are provided with sliding grooves, and the upper ends of the front and rear frames and the fixed rods are provided with sliders; the fixed frame, the front and rear frames, and the left and right frames slide relative to each other through the sliding grooves and sliders.

[0013] Preferably, the sliding assembly includes a drive shaft, a bushing, a drive wheel, a drive rack, a torsion spring, and a delay mechanism; the drive shaft is fixedly mounted to the motor, a drive block is provided on the drive shaft, and a bushing is slidably mounted on the drive shaft; a drive groove is provided on the bushing, and symmetrical locking blocks are provided on the bushing; drive wheels are symmetrically provided on both sides of the bushing, and the drive wheels are rotatably mounted in the adjustment cavity, each drive wheel having a locking groove; when the motor rotates, it drives the drive shaft to rotate synchronously, and the drive shaft pushes the drive groove through the drive block, thereby driving the bushing to slide up and down; drive racks are symmetrically provided on both sides of the drive wheel, with the upper drive rack and the lower drive rack being perpendicularly arranged; the upper and lower drive racks are fixedly connected to the front and rear frames and the left and right frames, respectively; when the drive wheel rotates, it meshes with the drive rack, thereby causing the drive rack... Sliding occurs, causing the front and rear frames or left and right frames to slide relative to each other via the drive rack, thus adjusting the sliding frame and causing the fixed suction cup to slide, changing the layout of the fixed suction cup. Both drive wheels are equipped with torsion springs between themselves and the inner wall of the adjustment cavity, and a delay mechanism is provided between the two torsion springs. The delay mechanism delays the reset of the drive wheels, and the torsion springs enable the drive wheels to reverse and reset. When both the front and rear frames need to be adjusted, the bushing first slides upward to drive the front and rear frames for adjustment. After the front and rear frames are adjusted, the motor reverses to drive the bushing to slide vertically downward. The bushing enters the lower drive wheel. At this time, the delay mechanism prevents the upper drive wheel from resetting, keeping the drive wheel fixed. The bushing continues to slide downward and engages with the lower drive wheel, thereby driving the lower drive wheel to rotate and complete the adjustment of the left and right frames.

[0014] Preferably, the delay mechanism includes a delay block, a reciprocating spring, and a push rod. The delay block is slidably mounted in the adjustment cavity via the reciprocating spring, and a push rod is provided below the delay block. The push rod is fixedly connected to the bushing and is located inside the circumference of the slot. Positioning slots are evenly distributed on the push rod, and positioning blocks are provided on the sliders of the front and rear frames. In the initial state, the upper end of the bushing is coplanar with the lower end face of the upper drive wheel, and the lower end of the bushing is located inside the lower drive wheel. At this time, the push rod presses the delay block inside the inner wall of the adjustment cavity, and the lower end of the delay block is coplanar with the upper end face of the upper drive wheel. When the bushing slides downward, the push rod moves downward synchronously, and the push rod no longer presses the delay block. The delay block slides into the slot of the upper drive wheel under the action of the reciprocating spring, thereby preventing the drive wheel from rotating and thus preventing the drive wheel from reversing and resetting.

[0015] Preferably, the adjustment assembly includes a movable block, a limiting rod, a return spring, and a push rod. The movable blocks are linearly arrayed between the front and rear frames and the fixed frame. The movable blocks, the front and rear frames, and the fixed frame are connected by the limiting rod. When the front and rear frames slide, the limiting rod drives the movable blocks to slide synchronously. A movable suction cup is slidably mounted on the slider. The movable suction cup is connected to the lower end of the slider by the return spring. A push groove is provided at the top of the movable suction cup, and a push rod is provided on one side of the movable suction cup. The push rod is fixedly installed in the fixed frame. The push rod has a squeezing groove that cooperates with the movable suction cup. Positioning grooves are evenly distributed on the push rod. Positioning blocks are provided on the sliders of the front and rear frames. When the movable block slides, it drives the movable suction cup to move synchronously. The push groove on the movable suction cup is pushed downward and extended by the squeezing groove on the push rod, thereby increasing the adsorption area of ​​the vacuum suction cup and enhancing the adsorption force according to the size of the goods. The return spring is used to realize the reset of the movable rod. The cooperation of the positioning groove and the positioning block ensures the stability of the sliding of the front and rear frames.

[0016] Preferably, the limiting rod is divided into an inner rod and an outer rod. The inner rod is slidably installed inside the outer rod. A limiting ring is provided on the inner side of the outer rod's circumference, and a limiting stop ring that cooperates with the outer rod is provided on the outer side of the inner rod's circumference. When the front and rear frames slide, they drive the outer rod to slide synchronously. After the outer rod slides a certain distance relative to the inner rod, the limiting ring on the outer rod engages with the limiting stop ring on the inner rod, thereby causing the outer rod to pull the inner rod to slide synchronously. This, in turn, causes the inner rod to pull adjacent movable blocks to slide synchronously, achieving the sliding of the movable blocks one by one, thus increasing the adsorption area.

[0017] Compared with the prior art, the beneficial effects of the present invention are: A robotic stacking device and stacking method are disclosed. The invention achieves the change of vacuum suction cup position and adsorption area through sliding components and adjusting components, realizing the uniformity of vacuum suction cup layout, adsorption force and cargo size, ensuring stacking quality and improving stacking efficiency.

[0018] A stacking device and method for robotic arms are disclosed. The present invention realizes the sequential sliding and resetting of the front and rear frames and the left and right frames through a sliding component, which ensures the stability of the fixed suction cup layout adjustment, thereby ensuring the stability of the fixed suction cup adjustment and ensuring the suction force.

[0019] A robotic stacking device and stacking method are disclosed. The present invention realizes the reciprocating sliding of the movable suction cup by adjusting the component, thereby following the sliding distance of the front and rear frames, synchronously increasing the adsorption area, ensuring the uniformity of adsorption force and cargo size, and thus ensuring the stability of stacking. Attached Figure Description

[0020] Figure 1 This is a flowchart of the stacking method of the present invention; Figure 2 This is a schematic diagram of the stacking device of the present invention; Figure 3 This is a schematic diagram of the overall fixing frame of the present invention; Figure 4 This is a half-sectional schematic diagram of the fixing frame of the present invention; Figure 5 For the present invention Figure 4 A magnified view of point A; Figure 6 For the present invention Figure 4 A magnified view of point B; Figure 7 This is a half-sectional schematic diagram of the sliding frame of the present invention; Figure 8 This is a schematic diagram of the sliding component and the adjusting component of the present invention; Figure 9 This is a half-sectional schematic diagram of the sliding component of the present invention; Figure 10 For the present invention Figure 9 A magnified view of point C; Figure 11 This is an exploded view of the sliding component of the present invention; Figure 12 This is a schematic diagram of the overall adjustment component of the present invention; Figure 13 This is a cross-sectional view of the adjustment component of the present invention; Figure 14 This is a cross-sectional view of the limiting tie rod of the present invention.

[0021] In the picture: 1. The robotic arm itself; 2. Mounting frame; 21. Vacuum pump; 22. Adjustment chamber; 3. Motor; 4. Sliding assembly; 41. Drive shaft; 411. Drive block; 42. Bushing; 421. Drive groove; 422. Locking block; 43. Drive wheel; 431. Locking groove; 44. Drive rack; 45. Torsion spring; 46. Delay mechanism; 461. Delay block; 462. Reciprocating spring; 463. Push rod; 5. Sliding frame; 51. Front and rear frames; 511. Positioning block; 52. Left and right frames; 521. Fixing rod; 522. Telescopic rod; 53. Slide groove; 54. Sliding block; 6. Vacuum suction cup; 61. Fixed suction cup; 62. Movable suction cup; 621. Push groove; 7. Adjustment component; 71. Movable block; 72. Limiting rod; 721. Inner rod; 7211. Limiting pull ring; 722. Outer rod; 7221. Limiting retaining ring; 73. Return spring; 74. Push rod; 741. Extrusion groove; 742. Positioning groove. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] The stacking robot for wooden doors mainly consists of a robot arm and an end effector. The end effector often adopts a vacuum adsorption mechanism, which uses a suction cup of the vacuum adsorption device to adhere to the surface of the wooden door. Then, a vacuum pump is used to create a vacuum and generate negative pressure, which makes the wooden door and the suction cup tightly bonded. Then, the multi-degree-of-freedom movement of the robot arm drives the wooden door to be placed in the designated position to complete the stacking.

[0024] Vacuum adsorption is a customized small vacuum system that uses a vacuum pump to create negative pressure by drawing air from the suction cup. It integrates components such as a vacuum pump, air tank, power controller, and vacuum sensor, featuring a robust, compact structure and stable operation. During operation, the system maintains an effective vacuum environment by adjusting the vacuum pump flow rate; the theoretical adsorption force is directly proportional to the vacuum level and the suction cup area. The equipment configuration includes single-pump or dual-pump combinations, driven by a 0.75kW motor, with a buffer tank capacity of up to 60L and a vacuum pumping speed of up to 20m³ / h. The control system supports variable frequency speed regulation and dual-pump linkage modes, and is equipped with an inflatable electromagnetic check valve to prevent oil return failure. Some systems integrate a liquid level monitoring module and a compressed air drainage device. The intelligent adsorption module monitors pressure fluctuations at a frequency of 1kHz using a piezoelectric sensor, achieving a 50ms-level rapid response in conjunction with a PLC. The vacuum level adjustment range covers -70kPa to -80kPa. This system can deeply integrate hydraulic drive, high-negative-pressure vacuum adsorption, and real-time motion tracking technologies based on multi-sensor fusion sensing and intelligent decision-making algorithms.

[0025] However, the position of the suction cups in existing vacuum adsorption devices cannot be adjusted in real time. When the size of the wooden door changes, the suction cups need to be manually removed from the bracket and their positions adjusted so that the layout of the suction cups matches the size of the wooden door, resulting in low stacking efficiency.

[0026] The present invention provides a technical solution: like Figures 1 to 14 As shown, a robotic stacking device and stacking method include: like Figure 1 As shown, a stacking method using a robotic arm includes the following steps: Step 1: Construct a model of the robotic stacking device and its working environment; Step 2: Set the initial and final position parameters and the moving step size of the robotic stacking device; Step 3: Perform global path planning based on the RRT algorithm; Step 4: The robotic stacking device stacks data based on a global path; Specifically, a kinematic model and a working environment model of the robotic stacking device are constructed to provide a foundation for subsequent path planning. The kinematic model combines forward and inverse kinematics theories to determine the accurate pose relationship between the base coordinates of the robotic stacking device and the end effector of the robotic arm. The initial position of the goods and the endpoint to be stacked are set, and the movable distance of the robotic stacking device is provided to provide a data basis for path planning. The RRT algorithm is a fast expanding random tree algorithm, which is an incremental path planning algorithm based on random sampling. It grows a tree structure from the starting point to random sampling points, quickly explores and connects to the target point in a high-dimensional non-convex space. The coordinates of the initial position of the goods are used as the starting point and the coordinates of the goods to be transported are used as the endpoint. The movable step size of the robotic stacking device is used to construct the node distance, and then a movement path is randomly generated. The generated path is locally optimized for obstacle avoidance planning. The robotic stacking device obtains the optimized global path and stacks the goods to complete the work.

[0027] In this embodiment, step 3 further includes the following steps: Step 3.1: Use RRT to obtain the initial and final positions and movement step size for global path planning; Step 3.2: Perform local path optimization based on the artificial potential field method; Step 3.3: Import the final optimized path into the global path for replacement; Specifically, starting from the initial coordinates of the goods and ending at the coordinates where the goods need to be moved, the node distance is constructed using the movable step length of the robotic stacking device, and then a movement path is randomly generated. The artificial potential field method optimizes the global path randomly generated by the RRT algorithm, reduces redundant nodes, improves the movement efficiency of the robotic stacking device, and ensures stacking efficiency. The optimized path replaces the path in the corresponding area of ​​the global path, thereby generating an efficient and convenient global path.

[0028] In this embodiment, step 3.2 further includes the following steps: Step 3.2.1: Determine if there are redundant nodes in the global path; Step 3.2.2: If there are no redundant nodes, the data is transmitted to the robotic stacking device as the final path. Step 3.2.3: If redundant nodes exist, import the start and end positions of the redundant nodes into the artificial potential algorithm. Step 3.2.4: The artificial potential algorithm generates an optimized path based on the start and end positions of redundant nodes; Specifically, the RRT algorithm performs random sampling based on a random strategy. As the algorithm progresses, the number of samplings increases, the number of branches and leaf nodes in the random tree increases, and the complexity of the random tree also increases. Therefore, redundant nodes may appear, which need to be judged. If there are no redundant nodes, the path plan generated by the RRT algorithm is directly imported into the robotic stacking device as a global path for stacking goods. If there are redundant nodes, the road segment data of the redundant nodes is sent to the artificial potential algorithm, which replans the path segment. The artificial potential algorithm completes path optimization based on the start and end positions and movement step size of the redundant nodes.

[0029] In this embodiment, step 3.3 further includes the following steps: Step 3.3.1: Determine if a collision has occurred in the current optimized path; Step 3.3.2: If no collision occurs, import the final optimized path into the global path for replacement. Step 3.3.3: If a collision occurs, return to the artificial potential algorithm to regenerate the optimized path; Specifically, the artificial potential algorithm performs obstacle avoidance judgment on the optimized path; if there are no obstacles on the optimized path, the optimized path is imported into the global path for replacement; if there are obstacles on the optimized path, the optimization result is returned to the artificial potential algorithm for replanning until there are no obstacles on the planned path trajectory, and then it is imported into the global path for replacement.

[0030] Figure 1 This is a flowchart of the stacking method of the present invention. The flowchart illustrates the path planning method of the robotic stacking device. By constructing a kinematic model and a working environment model of the robotic stacking device, a foundation is provided for subsequent path planning. Then, the initial position of the goods and the endpoint position to be stacked are set, and the movable distance of the robotic stacking device is provided as the data basis for path planning. The coordinates of the initial position of the goods are used as the starting point and the coordinates of the goods to be transported are used as the endpoint. The node distance is constructed using the movable step length of the robotic stacking device. Then, a movement path is randomly generated and obstacle avoidance planning is performed for local optimization of the generated path. The robotic stacking device obtains the optimized global path and stacks the goods to complete the work.

[0031] like Figures 2 to 14As shown, a robotic stacking device includes: a robotic arm body 1, a fixed frame 2, a motor 3, a sliding component 4, a sliding frame 5, a vacuum suction cup 6, and an adjusting component 7. The fixed frame 2 is fixedly mounted on the robotic arm body 1. A vacuum pump 21 is installed inside the fixed frame 2, and an adjusting cavity 22 is opened on the fixed frame 2. The motor 3 is fixedly mounted inside the adjusting cavity 22. The sliding component 4 is located below the motor 3 and is connected to the sliding frame 5. The sliding frame 5 is slidably mounted on the fixed frame 2. Vacuum suction cups 6 are provided on both the fixed frame 2 and the sliding frame 5. The vacuum suction cups 6 are connected to the vacuum pump 21 via flexible hoses. The vacuum suction cups 6 are divided into a fixed suction cup 61 and a movable suction cup 62. When the size of the goods changes, the motor 3 drives the sliding frame 5 to slide and change the position of the fixed suction cup 61 through the sliding component 4. An adjusting component 7 is located on the outer circumference of the sliding component 4 and is situated on the fixed frame 2. The adjusting component 7 is provided with a movable suction cup 62, and the sliding frame 5 drives the movable suction cup 62 to slide and adjust the suction force through the adjusting component 7. Specifically, a mounting frame 2 is fixedly installed on the robot body 1. The top of the mounting frame 2 has a mounting hole, through which the mounting frame 2 is fixedly installed to the end of the robot body 1. A vacuum pump 21 is installed inside the mounting frame 2, and an adjustment chamber 22 is provided on the mounting frame 2. A motor 3 is fixedly installed inside the adjustment chamber 22, and the motor 3 is located below the vacuum pump 21. A sliding assembly 4 is located below the motor 3, and the sliding assembly 4 is connected to a sliding frame 5. The sliding frame 5 is slidably installed on the mounting frame 2. Both the mounting frame 2 and the sliding frame 5 are equipped with vacuum suction cups 6, which are connected to the vacuum pump 21 via flexible hoses. The vacuum suction cups 6 are connected via flexible hoses (not shown in the figure). The vacuum pump 21 draws suction from the suction cups 6, creating an adhesive force to pick up the goods and stack them. The vacuum suction cups 6 consist of fixed suction cups 61 and movable suction cups 62. When the size of the goods changes, the motor 3 drives the sliding frame 5 via the sliding component 4 to slide and change the position of the fixed suction cups 61. When the size of the goods changes, the position of the suction cups needs to be adjusted to ensure uniform force distribution across the goods, thus preventing uneven force distribution that could cause the goods to shake or fall. When the size of the goods changes, motor 3 starts and drives sliding frame 5 to slide via sliding component 4. This, in turn, causes the fixed suction cups 61 fixedly connected to sliding frame 5 to move synchronously, thereby changing the position distribution of vacuum suction cups 6 to ensure uniform force distribution and stability of stacked goods of different sizes. Adjustment component 7 is located on the outer circumference of sliding component 4, on fixed frame 2. Adjustment component 7 has movable suction cups 62. Sliding frame 5 adjusts the suction force by driving movable suction cups 62 through adjustment component 7. As the size of the goods increases, the weight of the goods increases, requiring synchronous adjustment. The adsorption force is increased to ensure the stability of the adsorption of goods, thereby ensuring the stability of the goods stack. At this time, the sliding frame 5 will drive the movable suction cup 62 to slide out through the adjustment component 7 during the sliding process, so that the movable suction cup 62 contacts the goods, increasing the adsorption area of ​​the vacuum suction cup 6, thereby ensuring the stability of the adsorption of goods. The adsorption force of the vacuum suction cup 6 changes with the size of the goods. When the size of the goods increases, the weight and mass of the goods themselves increase. At this time, increasing the adsorption force will not cause the goods to be damaged due to excessive adsorption force, thus ensuring the stability and high quality of the stack.

[0032] In this embodiment, the sliding frame 5 includes front and rear frames 51 and left and right frames 52; a fixed suction cup 61 is installed on the fixed frame 2, the front and rear frames 51 and the left and right frames 52; the front and rear frames 51 are linearly arranged on the fixed frame 2, and the front and rear frames 51 are slidably connected to the fixed frame 2; multiple left and right frames 52 are linearly arranged on the front and rear frames 51, and the front and rear frames 51 are slidably connected to the left and right frames 52. Specifically, there are two front and rear frames 51, which slide symmetrically along the fixed frame 2, thereby adjusting the distance between them and the fixed frame 2. This causes the fixed suction cups 61 fixedly mounted on them to slide synchronously, changing their position in the front-to-back direction to accommodate goods of different sizes. There are also two left and right frames 52, used to adjust the position of the fixed suction cups 61 in the left-to-right direction of the fixed frame 2, thus changing the layout of the fixed suction cups 61 according to the size of the goods. Each left and right frame 52 includes a fixed rod 521 and a telescopic rod 522. The fixed rod 521 is fixedly connected to the fixed frame 2, and the telescopic rods 522 are slidably mounted at both ends of the fixed rod 521. The telescopic rods 522 are slidably connected to the front and rear frames 51. When the front and rear frames 51 slide horizontally, the front and rear frames 51 pull the telescopic rods 522 to slide synchronously, thereby changing the overall length of the left and right rods. This ensures that the left and right rods are positioned to match the front and rear frames 51, and the fixed rod 521 is fixedly connected to the fixed frame 2, thereby providing a fixed point for the sliding of the telescopic rod 522 and ensuring the overall stability of the telescopic rod 522 when it slides. The fixed frame 2 and the front and rear frames 51 are provided with a sliding groove 53 at their lower ends, and the front and rear frames 51 and the fixed rod 521 are provided with a slider 54 at their upper ends. The fixed frame 2, the front and rear frames 51 and the left and right frames 52 slide relative to each other through the sliding groove 53 and the slider 54. The fixed frame 2 is provided with a sliding groove 53 at its lower end, and the front and rear frames 51 are provided with a slider 54 that cooperates with the sliding groove 53 at their top ends. The front and rear frames 51 are slidably connected to the fixed rod 521 through the cooperation of the slider 54 and the sliding groove 53. The front and rear frames 51 are provided with a sliding groove 53 at their lower ends, and the telescopic rods 522 of the left and right rods are provided with sliders 54. The front and rear frames 51 drive the telescopic rod 522 to slide synchronously through the cooperation of the sliding groove 53 and the slider 54.

[0033] In this embodiment, the sliding assembly 4 includes a drive shaft 41, a bushing 42, a drive wheel 43, a drive rack 44, a torsion spring 45, and a delay mechanism 46. The drive shaft 41 is fixedly installed with the motor 3. A drive block 411 is provided on the drive shaft 41, and a bushing 42 is slidably installed on the drive shaft 41. A drive groove 421 is provided on the bushing 42, and symmetrically arranged locking blocks 422 are provided on the bushing 42. Drive wheels 43 are symmetrically arranged on both sides of the bushing 42, and the drive wheels 43 are rotatably mounted on the motor 3. Inside the adjustment cavity 22, a slot 431 is provided on the drive wheel 43; drive racks 44 are symmetrically arranged on both sides of the drive wheel 43, with the upper drive rack 44 and the lower drive rack 44 being arranged perpendicularly; the upper and lower drive racks 44 are fixedly connected to the front and rear frames 51 and the left and right frames 52, respectively; torsion springs 45 are provided between each of the two drive wheels 43 and the inner wall of the adjustment cavity 22, and a delay mechanism 46 is provided between the two torsion springs 45, the delay mechanism 46 being used to delay the reset of the drive wheel 43; Specifically, the drive shaft 41 is fixedly installed with the motor 3. A drive block 411 is provided on the drive shaft 41, and a bushing 42 is slidably installed on the drive shaft 41. A drive groove 421 is provided on the bushing 42, and symmetrical locking blocks 422 are provided on the bushing 42. Drive wheels 43 are symmetrically arranged on both sides of the bushing 42, and the drive wheels 43 are rotatably installed in the adjustment cavity 22. Locking grooves 431 are provided on the drive wheels 43. When the motor 3 rotates, it drives the drive shaft 41 to rotate synchronously. The drive shaft 41, through the drive block 411, pushes the drive groove 421, thereby causing the bushing 42 to slide up and down. When it is necessary to adjust the front and rear frames 51, the motor 3 rotates forward, thereby causing the bushing 42 to slide vertically upward. The locking blocks 422 of the bushing 42... The drive block 411 enters the slot 431 of the upper drive wheel 43, thus engaging with the upper drive block 411. At this time, the top of the drive block 411 is in contact with the top of the drive groove 421. When the motor 3 continues to rotate forward, the drive block 411 pushes the drive groove 421, thereby causing the bushing 42 to rotate. The bushing 42 drives the upper drive wheel 43 to rotate synchronously through the slot 422 and the drive block 422. When it is necessary for the left and right frames 52 to slide, the motor 3 reverses, thereby driving the drive shaft 41 to rotate synchronously. The drive shaft 41 pushes the bushing 42 to slide vertically downward through the drive block 411. The bushing 42 engages with the lower drive wheel 43 through the drive block 422. At this time, the drive block 411 and the drive groove 421 are in contact. One end is attached, and the drive shaft 41 continues to rotate, thereby driving the drive wheel 43 below to rotate; drive racks 44 are symmetrically arranged on both sides of the drive wheel 43, with the upper drive rack 44 and the lower drive rack 44 arranged perpendicularly; the upper and lower drive racks 44 are fixedly connected to the front and rear frames 51 and the left and right frames 52, respectively; when the drive wheel 43 rotates, it meshes with the drive racks 44, thereby causing the drive racks 44 to slide, thus driving the front and rear frames 51 or the left and right frames 52 to slide relative to each other, realizing the adjustment of the sliding frame 5, and thus driving the fixed suction cup 61 to slide, changing the layout of the fixed suction cup 61; a torsion spring 45 is provided between the drive wheel 43 and the inner wall of the adjustment cavity 22. A delay mechanism 46 is provided between the torsion springs 45. The delay mechanism 46 is used to delay the reset of the drive wheel 43. The torsion springs 45 are used to realize the reverse reset of the drive wheel 43. When it is necessary to adjust both the front and rear frames 51 and the left and right frames 52, the bushing 42 is first slid upward to drive the front and rear frames 51 for adjustment. After the front and rear frames 51 are adjusted, the motor 3 reverses to drive the shaft 41 sleeve to slide vertically downward. The bushing 42 enters the lower drive wheel 43. At this time, the delay mechanism 46 prevents the upper drive wheel 43 from resetting, so that the drive wheel 43 remains fixed. The bushing 42 continues to slide downward and engages with the lower drive wheel 43, thereby driving the lower drive wheel 43 to rotate to complete the adjustment of the left and right frames 52.

[0034] In this embodiment, the delay mechanism 46 includes a delay block 461, a reciprocating spring 462, and a push rod 463. The delay block 461 is slidably installed in the adjustment cavity 22 via the reciprocating spring 462, and the push rod 463 is provided below the delay block 461. The push rod 463 is fixedly connected to the bushing 42, and the push rod 463 is located on the inner side of the circumference of the slot 431. The push rod 74 has equidistantly distributed positioning slots 742, and the slider 54 of the front and rear frames 51 is provided with positioning blocks 511. Specifically, in the initial state, the upper end of the bushing 42 is coplanar with the lower end face of the upper drive wheel 43, and the lower end of the bushing 42 is located inside the lower drive wheel 43. At this time, the push rod 463 presses the delay block 461 located inside the inner wall of the adjustment cavity 22, and the lower end of the delay block 461 is coplanar with the upper end face of the upper drive wheel 43. When the bushing 42 slides downward, the push rod 463 moves downward synchronously, and the push rod 463 no longer presses the delay block 461. The delay block 461 slides into the slot 431 of the upper drive wheel 43 under the action of the reciprocating spring 462, thereby preventing the drive wheel 43 from rotating and thus preventing the drive wheel 43 from reversing and resetting. When the bushing 42 slides upward first to adjust the front and rear frames 51... After completion, the motor 3 reverses and drives the shaft 41 to slide vertically downward. Since the shaft sleeve 42 moves continuously, when the upper end face of the shaft sleeve 42 is flush with the lower end face of the upper drive wheel 43, the reciprocating spring 462 resets before the torsion spring 45 by setting the elastic modulus of the torsion spring 45 and the reciprocating spring 462. This causes the delay block 461 to enter the slot 431 of the upper drive wheel 43 and fix the upper drive wheel 43. When the work is completed and the shaft sleeve 42 returns to its initial position, the drive wheel 43 is no longer obstructed by the delay block 461, and the push rod 463 is located inside the circumference of the slot 431 and will not prevent the upper drive wheel 43 from resetting, thus completing the delayed reset.

[0035] In this embodiment, the adjustment component 7 includes a movable block 71, a limiting rod 72, a return spring 73, and a push rod 74. The movable block 71 is linearly arrayed between the front and rear frames 51 and the fixed frame 2. The movable block 71, the front and rear frames 51, and the fixed frame 2 are connected by the limiting rod 72. A movable suction cup 62 is slidably mounted on the slider 54. The movable suction cup 62 is connected to the lower end of the slider 54 by the return spring 73. A push groove 621 is provided at the top of the movable suction cup 62, and a push rod 74 is provided on one side of the movable suction cup 62. The push rod 74 is fixedly installed in the fixed frame 2. The push rod 74 is provided with a pressing groove 741 that cooperates with the movable suction cup 62. Positioning grooves 742 are evenly distributed on the push rod 74. A positioning block 511 is provided on the slider 54 of the front and rear frames 51. Specifically, movable blocks 71 are linearly arrayed between the front and rear frames 51 and the fixed frame 2. The movable blocks 71, the front and rear frames 51, and the fixed frame 2 are connected by limiting rods 72. The limiting rods 72 are telescopic, ensuring that the movable blocks 71 occupy a small length when retracted, while also ensuring sufficient sliding distance when dispersed. When the front and rear frames 51 slide, the limiting rods 72 drive the movable blocks 71 to slide synchronously. Simultaneously, the movable blocks 71 are connected to the fixed frame 2 via the limiting rods 72, providing a fixing force to prevent the movable blocks 71 from sliding along with the front and rear frames 51. This ensures that the limiting rod 72 of the previous movable block 71 is fully extended before the next movable block 71 slides. A movable suction cup 62 is slidably mounted on the slider 54, and the movable suction cup 62 is connected to the lower end of the slider 54 via a return spring 73. A push groove is provided at the top of the movable suction cup 62. 621, A push rod 74 is provided on one side of the movable suction cup 62; the push rod 74 is fixedly installed in the fixed frame 2, and the push rod 74 is provided with a squeezing groove 741 that cooperates with the movable suction cup 62. The push rod 74 is provided with positioning grooves 742 evenly distributed. The slider 54 of the front and rear frames 51 is provided with a positioning block 511. When the movable block 71 slides, it drives the movable suction cup 62 to move synchronously. The push groove 621 on the movable suction cup 62 is pushed downward and slides out by the squeezing groove 741 on the push rod 74, thereby increasing the adsorption area of ​​the vacuum suction cup 6, thereby enhancing the adsorption force according to the size of the goods. The return spring 73 is used to realize the return of the movable rod. The cooperation of the positioning groove 742 and the positioning block 511 ensures the stability of the sliding of the front and rear frames 51, and at the same time, it is used to realize the fixed distance sliding of the front and rear frames 51, thereby making the motor 3 rotate a full number of revolutions, thus ensuring that the slots 431 of the upper and lower drive wheels 43 always correspond, which facilitates the up and down sliding of the bushing 42.

[0036] In this embodiment, the limiting rod 72 is divided into an inner rod 721 and an outer rod 722. The inner rod 721 is slidably installed inside the outer rod 722. A limiting ring 7211 is provided on the inner side of the outer rod 722. A limiting stop ring 7221 that cooperates with the outer rod 722 is provided on the outer side of the inner rod 721. Specifically, when the front and rear frames 51 slide, they drive the outer rod 722 to slide synchronously. After the outer rod 722 slides a certain distance relative to the inner rod 721, the limiting pull ring 7211 on the outer rod 722 and the limiting stop ring 7221 on the inner rod 721 come into contact, thereby causing the outer rod 722 to pull the inner rod 721 to slide synchronously. In turn, the inner rod 721 pulls the adjacent movable blocks 71 to slide synchronously, thereby realizing the sliding of the movable blocks 71 one by one, which increases the adsorption area.

[0037] In use, the robotic stacking device of the present invention rotates forward, thereby driving the drive shaft 41 to rotate synchronously. The drive shaft 41, through the drive block 411, pushes the bushing 42 to slide vertically upward and engage with the upper drive wheel 43. At the same time, the top rod 463 pushes the delay block 461 to squeeze the reciprocating spring 462 into the adjustment cavity 22. When the bushing 42 slides upward to the top of the drive groove 421, the drive shaft 41 drives the bushing to rotate, thereby driving the upper drive wheel 43 to rotate and driving the torsion spring 45 to rotate synchronously. At the same time, the drive wheel 43 drives the upper drive rack 44 to slide symmetrically, thereby driving the front and rear frames 51 to slide horizontally. When the front and rear frames 51 slide, the limit rod 72 drives the movable block 71 to move synchronously. The movable block 71 drives the movable suction cup 62 to move synchronously. The movable suction cup 62, through the cooperation of the push groove 621 and the squeeze groove 741, pulls the reset spring 73 to slide downward and extend to be coplanar with the fixed suction cup 61. At the same time, the front and rear frames 51 pull the telescopic rod 522 to slide synchronously, thereby driving the fixed suction cup 61 to adjust its own position. When the distance adjustment of the front and rear frame 51 is completed and the left and right frames 52 need to be adjusted, the motor 3 reverses and drives the drive shaft 41 sleeve to slide vertically downward through the drive shaft 41. The bushing 42 drives the push rod 463 to move synchronously. The delay block 461 is no longer squeezed and pushed by the push rod 463, and then slides out under the action of the reciprocating spring 462. When the upper end face of the bushing 42 is flush with the lower end face of the upper drive wheel 43, the delay block 461 enters the slot 431 of the upper drive wheel 43 under the action of the reciprocating spring 462 to fix the upper drive wheel 43. The bushing 42 continues to slide downward and fully engages with the lower drive wheel 43. Then, it rotates under the action of the drive shaft 41. The lower drive wheel 43 rotates and the torsion spring 45 rotates. At the same time, it drives the lower drive rack 44 to slide. The drive rack 44 drives the fixed rod 521 to slide in the center. The fixed rod 521 pulls the telescopic rod 522 to slide synchronously and adjust the layout of the fixed suction cup 61. After the goods of this size are stacked, the motor 3 rotates forward and drives the bushing 42 to slide vertically upward through the drive shaft 41. When the bushing 42 is completely disengaged from the lower drive wheel 43, it partially gets stuck in the upper drive wheel 43. The lower drive wheel 43 reverses, thereby driving the left and right frames 52 to reset. After the left and right frames 52 are reset, the motor 3 reverses and drives the bushing 42 to return to its initial position through the drive shaft 41. The upper drive wheel 43 is no longer obstructed by the locking block 422 and the delay block 461. Under the action of the torsion spring 45, it reverses and resets, realizing the sequential reset of the left and right frames 52 and the front and rear frames 51, avoiding interference caused by simultaneous reset and increasing wear. When the front and rear frames 51 are reset, they drive the telescopic rods 522 of the left and right frames 52 to reset synchronously. At the same time, the front and rear frames 51 push the movable block 71 to reset through the limit pull rod 72. The movable block drives the movable suction cup 62 to reset. The movable suction cup 62 is no longer in contact with the push rod 74. The movable suction cup 62 is reset under the action of the reset spring 73.

[0038] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention 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 invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A stacking method using a robotic arm, characterized in that, Includes the following steps: Step 1: Construct a model of the robotic stacking device and its working environment; Step 2: Set the initial and final position parameters and the moving step size of the robotic stacking device; Step 3: Perform global path planning based on the RRT algorithm; Step 4: The robotic stacking device stacks data based on a global path.

2. The stacking method according to claim 1, characterized in that, Step 3 also includes the following steps: Step 3.1: RRT obtains the initial and final positions and motion compensation for global path planning; Step 3.2: Perform local path optimization based on the artificial potential field method; Step 3.3: Import the final optimized path into the global path for replacement.

3. The stacking method according to claim 2, characterized in that, Step 3.2 also includes the following steps: Step 3.2.1: Determine if there are redundant nodes in the global path; Step 3.2.2: If there are no redundant nodes, the data is transmitted to the robotic stacking device as the final path. Step 3.2.3: If redundant nodes exist, import the start and end positions of the redundant nodes into the artificial potential algorithm. Step 3.2.4: The artificial potential algorithm generates an optimized path based on the start and end positions of redundant nodes.

4. The stacking method according to claim 2, characterized in that, Step 3.3 also includes the following steps: Step 3.3.1: Determine if a collision has occurred in the current optimized path; Step 3.3.2: If no collision occurs, import the final optimized path into the global path for replacement. Step 3.3.3: If a collision occurs, return to the artificial potential algorithm to regenerate the optimized path.

5. A robotic stacking device, employing the stacking method according to any one of claims 1-4, characterized in that, include: The robotic arm body (1), the fixed frame (2), the motor (3), the sliding assembly (4), the sliding frame (5), the vacuum suction cup (6), and the adjustment assembly (7); A fixed frame (2) is fixedly installed on the main body (1) of the robotic arm; a vacuum pump (21) is provided inside the fixed frame (2), and an adjustment cavity (22) is opened on the fixed frame (2), and a motor (3) is fixedly installed inside the adjustment cavity (22); Below the motor (3) is a sliding component (4), which is connected to the sliding frame (5). The sliding frame (5) is slidably mounted on the fixed frame (2). Both the fixed frame (2) and the sliding frame (5) are equipped with vacuum suction cups (6). The vacuum suction cups (6) are connected to the vacuum pump (21) through a hose. The vacuum suction cups (6) are divided into fixed suction cups (61) and movable suction cups (62). When the size of the goods changes, the motor (3) drives the sliding frame (5) through the sliding component (4) to slide and change the position of the fixed suction cup (61). An adjustment component (7) is provided on the outer circumference of the sliding component (4). The adjustment component (7) is located on the fixed frame (2). The adjustment component (7) is equipped with a movable suction cup (62). The sliding frame (5) drives the movable suction cup (62) through the adjustment component (7) to slide and adjust the suction force.

6. The stacking device according to claim 5, characterized in that: The sliding frame (5) includes front and rear frames (51) and left and right frames (52); The fixed frame (2), front and rear frames (51) and left and right frames (52) are equipped with fixed suction cups (61); The front and rear frames (51) are linearly arrayed on the fixed frame (2), and the front and rear frames (51) are slidably connected to the fixed frame (2); The front and rear frames (51) have multiple left and right frames (52) arranged in a linear array, and the front and rear frames (51) are slidably connected to the left and right frames (52); The left and right frames (52) include a fixed rod (521) and a telescopic rod (522). The fixed rod (521) is fixedly connected to the fixed frame (2). The telescopic rod (522) is slidably installed at both ends of the fixed rod (521). The telescopic rod (522) is slidably connected to the front and rear frames (51). The lower ends of the fixed frame (2) and the front and rear frames (51) are provided with sliding grooves (53), and the upper ends of the front and rear frames (51) and the fixed rod (521) are provided with sliders (54).

7. The stacking device according to claim 6, characterized in that: The sliding assembly (4) includes a drive shaft (41), a bushing (42), a drive wheel (43), a drive rack (44), a torsion spring (45), and a delay mechanism (46). The drive shaft (41) is fixedly installed with the motor (3), and a drive block (411) is provided on the drive shaft (41). A bushing (42) is slidably installed on the drive shaft (41). The bushing (42) has a drive groove (421), and the bushing (42) has symmetrically arranged locking blocks (422). The bushing (42) has symmetrically arranged drive wheels (43) on both sides. The drive wheels (43) are rotatably installed in the adjustment cavity (22). The drive wheels (43) have locking grooves (431). The drive wheel (43) is symmetrically provided with drive racks (44) on both sides, and the upper drive rack (44) and the lower drive rack (44) are arranged perpendicularly; the upper and lower drive racks (44) are fixedly connected to the front and rear frames (51) and the left and right frames (52) respectively; Both drive wheels (43) are provided with torsion springs (45) between them and the inner wall of the adjustment cavity (22). A delay mechanism (46) is provided between the two torsion springs (45) for delaying the reset of the drive wheels (43).

8. The stacking device according to claim 7, characterized in that: The delay mechanism (46) includes a delay block (461), a reciprocating spring (462), and a push rod (463). The delay block (461) is slidably installed in the adjustment cavity (22) by a reciprocating spring (462), and a top rod (463) is provided below the delay block (461). The push rod (463) is fixedly connected to the bushing (42), and the push rod (463) is located inside the circumference of the slot (431).

9. The stacking device according to claim 7, characterized in that: The adjustment assembly (7) includes a movable block (71), a limiting rod (72), a return spring (73), and a push rod (74). The movable blocks (71) are linearly arrayed between the front and rear frames (51) and the fixed frame (2), and the movable blocks (71), the front and rear frames (51) and the fixed frame (2) are connected by limiting rods (72); A movable suction cup (62) is slidably mounted on the slider (54). The movable suction cup (62) is connected to the lower end of the slider (54) through a return spring (73). A push groove (621) is provided at the top of the movable suction cup (62), and a push rod (74) is provided on one side of the movable suction cup (62). The push rod (74) is fixedly installed in the fixed frame (2). The push rod (74) is provided with a squeezing groove (741) that cooperates with the movable suction cup (62). The push rod (74) is provided with positioning grooves (742) evenly distributed. The slider (54) of the front and rear frames (51) is provided with positioning blocks (511).

10. The stacking device according to claim 9, characterized in that: The limiting rod (72) is divided into an inner rod (721) and an outer rod (722). The inner rod (721) is slidably installed inside the outer rod (722). A limiting ring (7211) is provided on the inner side of the outer rod (722), and a limiting retaining ring (7221) that cooperates with the outer rod (722) is provided on the outer side of the inner rod (721).

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