Ball cage type parallel robot joint

Abstract

The invention relates to the technical field of robot joints, in particular to a ball cage type parallel robot joint which comprises a first supporting plate and a second supporting plate which are of the same structure and are arranged in the middles of the side faces of the periphery of a base assembly correspondingly, and driving shafts are rotationally arranged in the middles of the tops of the first supporting plate and the second supporting plate correspondingly; and the driving shaft is composed of a first rotating shaft and a second rotating shaft, the middle position of the second rotating shaft is fixedly sleeved with an input end, the input end is located at the top of the second supporting plate, and the outer end of the first rotating shaft is rotationally sleeved with a U-shaped swing arm. Through the arrangement of the driving shaft, the ball cage seat assembly, the U-shaped swing arm, the retainer and other parts and the compact size of all the structures, the effects that the device can be suitable for small-space joints of the humanoid robot, the friction force of the joints is reduced, and the flexibility of the device is improved are achieved, and the problem that due to the fact that the joints are large in size, the size is large is solved. However, the structure at the cross intersection point is bloated.

Description

Technical Field

[0001] This application relates to the technical field of robot joints, and in particular to a ball-cage type parallel robot joint. Background Technology

[0002] Robot joints are commonly classified into single-degree-of-freedom (DOF) joints, two-degree-of-freedom (DDF) joints, and three-degree-of-freedom (DDF) joints based on the number of degrees of freedom. The neck, shoulder, wrist, ankle, and waist are all three-degree-of-freedom joints. Three-degree-of-freedom joints can be constructed in series, parallel, or series-parallel configurations. Sometimes, for accuracy and convenience, it is required that the three rotational axes intersect at a single point. In this case, the most commonly used scheme is a single-degree-of-freedom series joint combined with a cross-shaped two-degree-of-freedom parallel joint.

[0003] In a cross-shaped parallel configuration with two degrees of freedom, the motor is typically placed at the intersection point.

[0004] A search revealed Chinese Patent Publication No. CN119610202A, which discloses a wrist joint mechanism, an arm structure, and a robot, including a transfer assembly; a first connecting assembly rotatably connected to the transfer assembly, the first connecting assembly rotating relative to the transfer assembly about a first axis; a first driving assembly disposed on the first connecting assembly; a link assembly, one end of which is connected to the output end of the first driving assembly, and the other end of which is connected to the transfer assembly; a second driving assembly disposed on the transfer assembly; and a second connecting assembly connected to the output end of the second driving assembly, the second driving assembly driving the second connecting assembly to rotate relative to the transfer assembly about a second axis; the first axis and the second axis intersect. The technical solution provided in this application makes the wrist joint mechanism more compact, thereby reducing the space occupied by the wrist joint mechanism in the arm structure.

[0005] Regarding the aforementioned technologies, the inventors have discovered the following drawbacks: while this simplifies the form of the structure and results in larger joint dimensions, it leads to a bulky structure at the intersection points.

[0006] The most common way to mount the motor outside the cross-shaped structure is to use a spatial linkage structure.

[0007] A search revealed Chinese Patent Publication No. CN223199056U, which discloses a connecting structure, a transmission device, a transmission assembly, an intelligent service system, an intelligent mobile system, and an intelligent terminal. The first mounting base is provided with a first mounting position and a second mounting position spaced apart along a second direction. The second mounting base is rotatably connected to the first mounting base around a first axis along the first direction and a second axis along a third direction. A linkage mechanism is rotatably connected to the second mounting base. In this invention, the first joint module and the second joint module are assembled within the connecting structure. Controlling the linkage mechanism to exhibit different motion changes drives the second mounting base to rotate around the first axis and / or the second axis, thereby increasing the degrees of freedom of the joint assembly and improving its flexibility.

[0008] Regarding the aforementioned technologies, the inventors discovered the following drawbacks: although the volume at the intersection point is small, the range of motion of the connecting rod is still very large, resulting in a bulky structure. Summary of the Invention

[0009] To address the problems mentioned in the background section, this application provides a ball-cage type parallel robot joint.

[0010] This application provides a ball cage type parallel robot joint, which adopts the following technical solution: two sets of identical first support plates and second support plates are respectively arranged at the middle positions of the four sides of the base assembly. A drive shaft is rotatably arranged at the middle position of the top of the first support plate and the second support plate. The drive shaft is composed of a first rotating shaft and a second rotating shaft. An input end is fixedly sleeved at the middle position of the second rotating shaft, and the input end is located at the top of the second support plate. A U-shaped swing arm is rotatably sleeved at the outer end of the first rotating shaft. A ball cage type universal joint mechanism is arranged on the outside of the drive shaft. The ball cage type universal joint mechanism is connected to the U-shaped swing arm in a transmission connection.

[0011] Optionally, the ball cage universal joint mechanism includes a first arc-shaped groove on the outside of the drive shaft, a ball cage seat assembly, a cage and balls. There are six first arc-shaped grooves, which are evenly distributed in a semi-circle on the outside of the drive shaft. A ball is slidably disposed on the inner wall of each first arc-shaped groove. The cage is sleeved on the middle of the outside of the drive shaft. The inner and outer walls of the cage are both spherical structures. Six receiving holes are opened in the middle of the cage corresponding to the position of the balls. The balls are rotated and engaged in the receiving holes.

[0012] Optionally, the ball cage assembly is composed of hemispherical cage A and hemispherical cage B connected together. The interiors of hemispherical cage A and hemispherical cage B together form an inner spherical structure and are respectively adapted to the outer spherical surface of the cage. A fourth arc-shaped groove is provided on the inner side of hemispherical cage A corresponding to the position of the ball, and a second arc-shaped groove is provided on the inner side of hemispherical cage B corresponding to the position of the ball. The inner walls of the fourth arc-shaped groove and the second arc-shaped groove are slidably connected to the outer side of the ball.

[0013] Optionally, a first connecting shaft is integrally formed near the top of hemispherical cage A, and a first connecting hole is provided on the first connecting shaft. A second connecting shaft is integrally formed near the top of hemispherical cage B, and a second connecting hole is provided on the second connecting shaft. Hemispherical cage A and hemispherical cage B are fixedly connected by fasteners passing through the first connecting hole and the second connecting hole.

[0014] Optionally, a third arc-shaped groove is recessed inward at the middle of the top of the U-shaped swing arm. The U-shaped swing arm is sleeved on the outside of the two first support plates. The first connecting shaft and the second connecting shaft are both semi-cylindrical structures. After they are joined together, they form a complete cylinder. A collar is sleeved on the outside of the cylinder. The collar is slidably connected to the inner wall of the third arc-shaped groove. The width of the inner wall of the third arc-shaped groove is greater than the diameter of the cylinder after joining.

[0015] Optionally, pulleys are fixedly fitted on the outer sides of both the first and second rotating shafts. The pulleys are connected to the output end of an external drive motor via a transmission belt. The external drive motor is fixedly installed below the base assembly and drives the drive shaft to rotate around its own axis via the transmission belt, thereby causing the ball cage assembly to swing around the second rotating shaft.

[0016] Optionally, the cage is made of high-strength alloy material, and the inner wall of its receiving hole is provided with a lubricating coating, which is a polytetrafluoroethylene coating, to reduce the coefficient of friction between the ball and the receiving hole.

[0017] Optionally, the inner walls of the first, second, third, and fourth arc-shaped grooves are all polished to reduce wear when in contact with balls or collars.

[0018] Optionally, the ball cage universal joint mechanism, which is composed of the base assembly, drive shaft, ball cage seat assembly, cage and ball, has two rotational degrees of freedom: the rotational degree of freedom of the drive shaft along its own axis and the swinging degree of freedom of the ball cage seat assembly around a second rotational axis.

[0019] In summary, this application includes the following beneficial technical effects: This invention, by setting up components such as a drive shaft, ball cage assembly, U-shaped swing arm, and cage, achieves a compact size among these structures, making the device suitable for use in the small joints of humanoid robots. This reduces joint friction and improves the device's flexibility, solving the problem of bulky structures at the intersection points caused by large joint sizes.

[0020] This invention improves contact stability and wear resistance, extends the service life of the ball cage assembly, and reduces usage costs by adding a collar between the outer surfaces of the two hemispherical cages, the rotating shaft, and the arc groove of the U-shaped swing arm. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the overall three-dimensional structure in the embodiments of this application; Figure 2 This is a schematic diagram of the three-dimensional exploded structure in the embodiments of this application; Figure 3 This is a schematic diagram of the three-dimensional structure of the arc-shaped groove on the surface of the drive shaft in an embodiment of this application; Figure 4 This is a schematic diagram of the three-dimensional structure of the cage in an embodiment of this application; Figure 5 This is a three-dimensional structural diagram of hemispherical cage A in an embodiment of this application; Figure 6 This is a schematic diagram of the three-dimensional structure of hemispherical cage B in the embodiments of this application; Figure 7 This is a schematic diagram of the outer front side structure in an embodiment of this application; Figure 8 This is a schematic diagram of the front cross-sectional structure in an embodiment of this application; Figure 9 This is a schematic diagram of the right side structure in an embodiment of this application; Figure 10 This is a schematic cross-sectional view of the structure on the right side in an embodiment of this application; Figure 11 This is a schematic diagram of the three-dimensional structure of the collar in the embodiment of this application.

[0022] Reference numerals: 1. Base assembly; 2. Drive shaft; 2.1. Input end; 2.2. First arc-shaped groove; 3. Ball cage seat assembly; 31. Hemispherical cage A; 31.1. Fourth arc-shaped groove; 31.2. First connecting shaft; 31.3. First connecting hole; 32. Hemispherical cage B; 32.1. Second arc-shaped groove; 32.2. Second connecting shaft; 32.3. Second connecting hole; 4. U-shaped swing arm; 4.1. Third arc-shaped groove; 5. Cage; 5.1. Receiving hole; 6. Ball; 7. Collar; Z1. First rotating shaft; Z2. Second rotating shaft; 8. First support plate; 9. Second support plate. Detailed Implementation

[0023] The following is in conjunction with the appendix Figure 1-11 This application will be described in further detail.

[0024] This application discloses a ball-cage type parallel robot joint. For example... Figure 1As shown, two sets of identical first support plates 8 and second support plates 9 are respectively arranged in the middle of the four sides of the base assembly 1. A drive shaft 2 is rotatably arranged in the middle of the top of the first support plate 8 and the second support plate 9. The drive shaft 2 consists of a first rotating shaft Z1 and a second rotating shaft Z2. An input end 2.1 is fixedly sleeved in the middle of the second rotating shaft Z2, and the input end 2.1 is located on the top of the second support plate 9. A U-shaped swing arm 4 is rotatably sleeved on the outer end of the first rotating shaft Z1. A ball cage universal joint mechanism is arranged on the outer side of the drive shaft 2. The ball cage universal joint mechanism is connected to the U-shaped swing arm 4 in a transmission connection.

[0025] By adopting the above technical solution, the above structure achieves a compact fit between the drive shaft 2 and the ball-cage universal joint mechanism. The components are rationally arranged and compact in size, enabling the overall joint structure to adapt to the installation requirements of humanoid robot joints in small spaces. At the same time, the transmission path is direct, effectively reducing the frictional resistance during joint movement and significantly improving the flexibility of joint movements.

[0026] The ball cage universal joint mechanism includes a first arc-shaped groove 2.2 on the outside of the drive shaft 2, a ball cage seat assembly 3, a cage 5, and balls 6. There are six first arc-shaped grooves 2.2, which are evenly distributed in a semi-circle on the outside of the drive shaft 2. The inner wall of each first arc-shaped groove 2.2 is slidably provided with balls 6. The cage 5 is sleeved on the middle of the outside of the drive shaft 2. The inner and outer walls of the cage 5 are both spherical structures. The middle part of the cage has six receiving holes 5.1 corresponding to the position of the balls 6. The balls 6 are rotatably engaged in the receiving holes 5.1.

[0027] By adopting the above technical solution, the spherical structure of the cage 4.1 third arc groove 5 and the matching design of the ball 6 enable stable transmission of each component in a limited space, further improving the structural compactness and making it suitable for small space installation scenarios. At the same time, the sliding contact between the ball 6 and the arc groove and the receiving hole 5.1 replaces the traditional rigid contact, greatly reducing friction. Combined with the precise positioning of the ball 6 by the cage 4.1 third arc groove 5, the joint movement is more flexible and avoids jamming.

[0028] The ball cage assembly 3 is composed of a hemispherical cage A31 and a hemispherical cage B32 joined together. The interiors of hemispherical cage A31 and hemispherical cage B32 together form an inner spherical structure, which is adapted to the outer spherical surface of the cage 5. A fourth arc-shaped groove 31.1 is provided on the inner side of hemispherical cage A31 corresponding to the position of the ball 6, and a second arc-shaped groove 32.1 is provided on the inner side of hemispherical cage B32 corresponding to the position of the ball 6. The inner walls of the fourth arc-shaped groove 31.1 and the second arc-shaped groove 32.1 are slidably connected to the outer side of the ball 6.

[0029] By adopting the above technical solution, the split structure of the two hemispherical cages is not only easy to assemble and maintain, but also the multi-contact transmission structure formed by the cage 4.1 third arc groove, 5, and ball 6 reduces the overall volume while ensuring transmission stability, making it suitable for use in small space joints. The matching design of the arc groove and ball 6 further optimizes the friction contact surface, reduces motion resistance, improves joint flexibility, and disperses force to reduce local wear.

[0030] The hemispherical cage A31 has a first connecting shaft 31.2 integrally formed near the top, and the first connecting shaft 31.2 has a first connecting hole 31.3. The hemispherical cage B32 has a second connecting shaft 32.2 integrally formed near the top, and the second connecting shaft 32.2 has a second connecting hole 32.3. The hemispherical cage A31 and the hemispherical cage B32 are fixedly connected by fasteners that pass through the first connecting hole 31.3 and the second connecting hole 32.3.

[0031] By adopting the above technical solution, the one-piece molded connecting shaft and the detachable fastener connection method not only ensure the structural strength of the ball cage assembly 3, but also simplify the installation process, making it easy to maintain each component in a compact layout. The stable connection structure ensures the accuracy of power transmission during the transmission process, reduces the additional friction and noise caused by loose components, improves the stability and flexibility of joint movement, and indirectly extends the service life of the joint.

[0032] The top of the U-shaped swing arm 4 has an inwardly recessed third arc-shaped groove 4.1. The U-shaped swing arm 4 is sleeved on the outside of the two first support plates 8. The first connecting shaft 31.2 and the second connecting shaft 32.2 are both semi-cylindrical structures. After they are joined together, they form a complete cylinder. The outer side of the cylinder is fitted with a collar 7. The collar 7 is slidably connected to the inner wall of the third arc-shaped groove 4.1. The width of the inner wall of the third arc-shaped groove 4.1 is greater than the diameter of the cylinder after joining.

[0033] By adopting the above technical solution, a collar 7 is installed between the connecting shaft of the two hemispherical cages and the arc groove of the second arc groove of the U-shaped swing arm 32.1 4. The collar 7 can fill the gap between the connecting shaft and the arc groove, improve the contact stability, and prevent shaking during movement. At the same time, the collar 7 can withstand the main frictional loss and effectively protect the main structure of the connecting shaft and the second arc groove of the U-shaped swing arm 32.1 4. This significantly improves the wear resistance and service life of the ball cage assembly, reduces subsequent maintenance and replacement costs, and, in conjunction with the semi-cylindrical docking structure, makes component assembly more convenient and further optimizes the installation efficiency in small spaces.

[0034] Both the first rotating shaft Z1 and the second rotating shaft Z2 are fixedly fitted with pulleys. The pulleys are connected to the output end of the external drive motor through a transmission belt. The external drive motor is fixedly installed below the base assembly 1 and drives the drive shaft 2 to rotate around its own axis through the transmission belt, thereby causing the ball cage assembly 3 to swing around the second rotating shaft Z2.

[0035] By adopting the above technical solution, the design of placing the drive motor below the base assembly 1 allows for spatial separation of the power source and the joint actuator, further reducing the volume of the joint body and adapting to the installation requirements of small spaces. The belt drive method has a buffering and shock absorption effect, which can reduce the impact of motor vibration on the joint movement accuracy. At the same time, the compact transmission structure makes the power transmission efficient and the friction loss low, improving the response speed and flexibility of the joint movement.

[0036] The cage 5 is made of high-strength alloy material, and the inner wall of its receiving hole 5.1 is provided with a lubricating coating, which is a polytetrafluoroethylene coating, to reduce the coefficient of friction between the ball 6 and the receiving hole 5.1.

[0037] By adopting the above technical solution, the high-strength alloy material makes the third arc groove 5 of the cage 4.1 less prone to deformation when subjected to the pressure of the ball 6, ensuring structural stability and extending service life. The polytetrafluoroethylene lubricating coating has excellent friction-reducing properties, which can further reduce the frictional resistance between the ball 6 and the receiving hole 5.1, making the joint movement more flexible, while reducing wear caused by friction, avoiding frequent lubrication maintenance, reducing usage costs, and meeting the needs of humanoid robot joints for long-term stable operation.

[0038] The inner walls of the first arc groove 2.2, the second arc groove 32.1, the third arc groove 4.1 and the fourth arc groove 31.1 are all polished to reduce wear when in contact with the ball 6 or the collar 7.

[0039] By adopting the above technical solution, the high-precision polishing process makes the inner wall of each arc groove smooth and flat, which greatly reduces the coefficient of friction when in contact with the ball 6 and collar 7. This not only improves the flexibility of joint movement and reduces power loss, but also reduces the wear of the contact surface. Combined with the protective function of the collar 7, it further extends the service life of each component, reduces the maintenance and replacement cost of the equipment, and ensures the long-term stable operation of the joint.

[0040] The ball cage universal joint mechanism, which is composed of base assembly 1, drive shaft 2, ball cage seat assembly 3, cage 5 and ball 6, has two rotational degrees of freedom: the rotational degree of freedom of drive shaft 2 along its own axis and the swinging degree of freedom of ball cage seat assembly 3 around the second rotation axis Z2.

[0041] By adopting the above technical solution, the dual rotational degrees of freedom design enables the joint to achieve more complex motion postures, meeting the needs of multi-dimensional movement of humanoid robot joints. The components that realize this degree of freedom adopt a compact layout, which ensures the range of motion without occupying too much space. Combined with a low-friction transmission structure, the joint can still remain flexible and stable during multi-degree-of-freedom movement, improving the accuracy and coordination of robot movements.

[0042] The implementation principle of a ball cage type parallel robot joint in this application embodiment is as follows: When the motor starts, the power is transmitted to the pulley via the belt, thereby driving the drive shaft 2 to rotate around its own axis. The drive shaft 2 achieves stable rotational connection with the base assembly 1 through the first support plate 8 and the second support plate 9. The input end 2.1 on the second rotating shaft Z2 can assist in the precise guidance of power transmission, ensuring the efficiency and stability of the initial power transmission. The rotational motion of the drive shaft 2 is converted and transmitted through the ball cage universal joint mechanism. This mechanism is composed of the first arc groove 2.2 on the outer side of the drive shaft 2, the ball cage seat assembly 3, the cage 5 and the ball 6 working together. It is the core unit for realizing the flexible movement of the joint, and its motion transmission is divided into three key links. The drive shaft 2 has six semi-circular first arc grooves 2.2 evenly distributed on its outer side. Each groove has a ball bearing 6 slidably disposed therein. The ball bearing 6 is simultaneously rotated and engaged in the receiving hole 5.1 in the middle of the cage 5. The cage 5 adopts an inner and outer spherical structure design. Its inner wall is adapted to the drive shaft 2, and its outer wall is adapted to the inner spherical surface of the ball cage assembly 3. When the drive shaft 2 rotates, the inner wall of the first arc groove 2.2 generates a circumferential thrust on the ball bearing 6. The cage 5 precisely limits the ball bearing 6 through the receiving hole 5.1 to prevent the ball bearing 6 from deviating. This allows the ball bearing 6 to roll along the arc groove trajectory, converting the rotational power of the drive shaft 2 into its own rolling transmission. The ball cage assembly 3 is composed of hemispherical cage A31 and hemispherical cage B32, which are fixedly connected by fasteners. The two form a complete inner spherical structure. The fourth arc groove 31.1 on the inner side of hemispherical cage A31 and the second arc groove 32.1 on the inner side of hemispherical cage B32 are respectively slidably connected to the outer side of ball 6. When ball 6 rolls, its outer side generates friction with the inner wall of the arc groove, which pushes the ball cage assembly 3 to move synchronously with the movement of ball 6. Due to the spherical constraint of cage 5 and the multi-directional rolling characteristics of ball 6, ball cage assembly 3 can realize the swinging motion around the second rotation axis Z2 while receiving power, thereby completing the motion conversion from drive shaft rotation to ball cage swinging, providing a multi-degree-of-freedom motion basis for the joint. The cage 5 is made of high-strength alloy material, which can withstand the pressure transmitted by the balls 6 without easily deforming. The polytetrafluoroethylene lubricating coating on the inner wall of its receiving hole 5.1 can reduce the coefficient of friction with the balls 6 and ensure smooth rolling of the balls. At the same time, the spherical structure of the cage 5 ensures that the balls 6 are always evenly distributed, avoiding jamming caused by uneven force during movement, and providing structural support for the stable transmission of the entire universal joint mechanism. The first connecting shaft 31.2 of the hemispherical cage A31 and the second connecting shaft 32.2 of the hemispherical cage B32 are both semi-cylindrical. After docking, they form a complete cylinder. The collar 7 sleeved on the outside of the collar is slidably connected to the third arc groove 4.1 at the top of the U-shaped swing arm 4. When the cage seat assembly 3 swings, the connecting shaft drives the collar 7 to slide along the inner wall of the third arc groove 4.1. The collar 7 fills the gap between the connecting shaft and the arc groove, preventing wobbling during movement, while bearing the main frictional loss and protecting the connecting shaft and the main body structure of the U-shaped swing arm 4. The ball cage universal joint mechanism, consisting of base assembly 1, drive shaft 2, ball cage assembly 3, cage 5, and ball bearings 6, ultimately achieves two core rotational degrees of freedom: first, the rotational degree of freedom of drive shaft 2 itself around its axis, directly driven by an external motor via a belt; second, the swinging degree of freedom of ball cage assembly 3 around the second rotational axis Z2, achieved by ball bearings 6 constrained by the arc groove and cage 5, converting the rotation of the drive shaft into multi-directional swinging of the ball cage. The combination of these two degrees of freedom enables the joint to perform complex posture adjustments, meeting the multi-dimensional motion requirements of humanoid robot joints. The compact layout of each component ensures that the joint can adapt to small-space installation scenarios while achieving multi-degree-of-freedom motion, reducing motion resistance and component wear, thus improving the joint's flexibility, extending its service life, and reducing maintenance costs.

[0043] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A ball-cage parallel robot joint comprising a base assembly (1), characterized in that: The base assembly (1) is provided with two groups of first support plates (8) and second support plates (9) which are the same in structure at the middle positions of the four side surfaces, the top of each of the first support plates (8) and the second support plates (9) is rotatably provided with a drive shaft (2), the drive shaft (2) is composed of a first rotation shaft (Z1) and a second rotation shaft (Z2), the middle position of the second rotation shaft (Z2) is fixedly sleeved with an input end (2.1), and the input end (2.1) is located at the top of the second support plate (9), the outer end of the first rotation shaft (Z1) is rotatably sleeved with a U-shaped swing arm (4), the outer side of the drive shaft (2) is provided with a ball cage type universal joint mechanism, and the ball cage type universal joint mechanism is in transmission connection with the U-shaped swing arm (4).

2. A ball-cage parallel robot joint according to claim 1, characterized in that: The ball cage type universal joint mechanism comprises first arc-shaped grooves (2.2) provided on the outer side of the drive shaft (2), a ball cage seat assembly (3), a retainer (5) and balls (6), the number of the first arc-shaped grooves (2.2) is six, and the first arc-shaped grooves (2.2) are uniformly distributed in a semicircular shape on the outer side of the drive shaft (2), the inner wall of each of the first arc-shaped grooves (2.2) is slidably provided with the ball (6), the retainer (5) is sleeved on the middle part of the outer side of the drive shaft (2), the inner and outer walls of the retainer (5) are spherical surface structures, and six accommodating holes (5.1) are formed in the middle part of the retainer (5) corresponding to the positions of the balls (6), and the ball (6) is rotatably clamped in the accommodating hole (5.1).

3. A ball-cage parallel robot joint according to claim 2, characterized in that: The ball cage seat assembly (3) is composed of a half ball cage A (31) and a half ball cage B (32), the interiors of the half ball cage A (31) and the half ball cage B (32) jointly form an inner spherical surface structure, and are matched with the outer spherical surface of the retainer (5) respectively, a fourth arc-shaped groove (31.1) is formed in the inner side of the half ball cage A (31) corresponding to the position of the ball (6), a second arc-shaped groove (32.1) is formed in the inner side of the half ball cage B (32) corresponding to the position of the ball (6), and the inner walls of the fourth arc-shaped groove (31.1) and the second arc-shaped groove (32.1) are slidably connected with the outer side of the ball (6).

4. A ball-cage parallel robot joint according to claim 3, characterized in that: The half ball cage A (31) is integrally formed with a first connecting shaft (31.2) close to the top position, a first connecting hole (31.3) is formed in the first connecting shaft (31.2), the half ball cage B (32) is integrally formed with a second connecting shaft (32.2) close to the top position, a second connecting hole (32.3) is formed in the second connecting shaft (32.2), and the half ball cage A (31) and the half ball cage B (32) are fixedly connected through the fastener penetrating the first connecting hole (31.3) and the second connecting hole (32.3).

5. A ball-cage parallel robot joint according to claim 4, characterized in that: The U-shaped swing arm (4) top middle position is provided with a third arc-shaped groove (4.1) which is inwardly recessed, the U-shaped swing arm (4) is sleeved on the outer side of two first support plates (8), the first connecting shaft (31.2) and the second connecting shaft (32.2) are both semi-cylindrical structures, and after being butted, a complete cylinder is formed, and the outer side of the cylinder is sleeved with a sleeve ring (7), the sleeve ring (7) is in sliding connection with the inner wall of the third arc-shaped groove (4.1), and the inner wall width of the third arc-shaped groove (4.1) is greater than the diameter of the cylinder after being butted.

6. A ball-cage parallel robot joint according to claim 1, characterized in that: The outer side of the first rotating shaft (Z1) and the second rotating shaft (Z2) is fixedly sleeved with a belt pulley, the belt pulley is in transmission connection with the output end of an external driving motor through a transmission belt, the external driving motor is fixedly installed below the base assembly (1), and the transmission belt drives the driving shaft (2) to rotate around its own axis, so as to drive the ball cage seat assembly (3) to swing around the second rotating shaft (Z2).

7. A ball-cage parallel robot joint according to claim 2, characterized in that: The retainer (5) is made of high-strength alloy material, the inner wall of the containing hole (5.1) is provided with a lubricating coating, the lubricating coating is a polytetrafluoroethylene coating, and is used for reducing the friction coefficient between the ball (6) and the containing hole (5.1).

8. A ball-cage parallel robot joint according to claim 3, characterized in that: The inner walls of the first arc-shaped groove (2.2), the second arc-shaped groove (32.1), the third arc-shaped groove (4.1) and the fourth arc-shaped groove (31.1) are polished to reduce wear when contacting the ball (6) or the sleeve ring (7).

9. A ball-cage parallel robot joint according to claim 1, characterized in that: The base assembly (1), the driving shaft (2), the ball cage seat assembly (3), the retainer (5) and the ball (6) jointly constitute a ball cage type universal joint mechanism which has two rotating degrees of freedom, which are the rotating degree of freedom of the driving shaft (2) and the swinging degree of freedom of the ball cage seat assembly (3) around the second rotating shaft (Z2).

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