Flexible joint and robotic arm

Abstract

The present application relates to the technical field of mechanical arm, provide a kind of flexible joint and mechanical arm, comprising: frame body, rotating first rotating table being disposed on the frame body around predetermined axis, motor being disposed on the frame body and having output shaft, second rotating table being disposed on the output shaft, and torsion spring;The output shaft rotates around the predetermined axis;In the extension direction of the predetermined axis, the first rotating table and the second rotating table are spaced apart, the torsion spring is arranged between the first rotating table and the second rotating table, the first rotating table is provided with first clamping slot, the second rotating table is provided with second clamping slot, the first clamping slot and the second clamping slot are respectively spaced apart between the predetermined axis, the first end of the torsion spring is clamped in the first clamping slot, and the second end of the torsion spring is clamped in the second clamping slot.

Description

Technical Field

[0001] This invention belongs to the field of robotic arm technology, and more specifically relates to a flexible joint and a robotic arm. Background Technology

[0002] In modern robots, bipedal robots (such as Atlas, a robot produced by Boston Dynamics) are quite common. Bipedal robots often rely on the power output of motors at their joints to jump. The joints of existing robots all rely on the power output of the motors themselves. Once the motors stop working, the power of the joints is cut off instantly, which seriously affects the continuity and explosive power of the joints.

[0003] The joint motor can be referenced in: (Chinese Invention Patent; Publication No.: CN108608458A; Subject Name: A Series-Driven Compliant Robotic Arm Joint; Publication Date: 2018-10-02). When the joint motor is de-energized, the joint stops moving and cannot continuously output power, resulting in weak explosive force.

[0004] For example, the joint motor can be referenced in: (Chinese Invention Patent; Publication No.: CN218217030U; Subject: A Joint Motor and Reducer; Publication Date: 2023.01.03). When the motor is powered off, the joint stops moving and cannot continuously output power, resulting in weak explosive force. Summary of the Invention

[0005] The purpose of this invention is to provide a flexible joint and a robotic arm equipped with the joint's transmission system, so as to solve the technical problem in the prior art that the joint cannot continuously output power after the power is cut off.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a flexible joint includes: a frame, a first rotating platform rotatably mounted on the frame about a predetermined axis, a motor mounted on the frame and having an output shaft, a second rotating platform mounted on the output shaft, and a torsion spring; the output shaft rotates about the predetermined axis; the first rotating platform and the second rotating platform are spaced apart in the extension direction of the predetermined axis, the torsion spring is disposed between the first rotating platform and the second rotating platform, a first slot is provided on the first rotating platform, a second slot is provided on the second rotating platform, the first slot and the second slot are spaced apart from the predetermined axis, a first end of the torsion spring is engaged in the first slot, and a second end of the torsion spring is engaged in the second slot.

[0007] Furthermore, in the circumferential direction surrounding the predetermined axis, the two side walls of the first slot are respectively located on the movement path of the first end of the torsion spring rotating around the predetermined axis.

[0008] Furthermore, in the circumferential direction surrounding the predetermined axis, the two side walls of the second slot are respectively located on the movement path of the second end of the torsion spring rotating around the predetermined axis.

[0009] Furthermore, a first boss and a second boss are provided on the inner wall of the first rotating platform facing the second rotating platform, and the first slot is formed between the first boss and the second boss.

[0010] Furthermore, the first boss is cylindrical, and / or the second boss is cylindrical.

[0011] Furthermore, a third protrusion and a fourth protrusion are provided on the inner wall of the second rotating platform facing the first rotating platform, and the second slot is formed between the third protrusion and the fourth protrusion.

[0012] Furthermore, the third boss is cylindrical, and / or the fourth boss is cylindrical.

[0013] Furthermore, a rod is provided on the first rotating platform, and the predetermined axis is the axis of the rod; the torsion spring is sleeved on the rod.

[0014] Furthermore, the frame is provided with positioning holes, and the rod is inserted into the positioning holes.

[0015] The present invention also provides a robotic arm, including: the flexible joint.

[0016] The beneficial effects of the flexible joint provided by this invention are as follows: Compared with the prior art, the flexible joint provided by this invention has a first rotating platform on the frame, which can rotate around a predetermined axis; a motor on the frame, which has an output shaft that can rotate around the predetermined axis; a second rotating platform on the output shaft, which drives the second rotating platform to rotate around the predetermined axis when the output shaft rotates; the first and second rotating platforms are spaced apart, and a torsion spring is disposed between the first and second rotating platforms, with the first end of the torsion spring engaged in a first slot on the first rotating platform and the second end engaged in a second slot on the second rotating platform. The first and second slots are spaced apart from the predetermined axis. When the motor drives the second rotating platform to rotate through the output shaft, the torque generated by the second rotating platform is transmitted to the first rotating platform through the torsion spring. The first slot on the rotating platform drives the first rotating platform to rotate. Power is transmitted between the first and second rotating platforms via a torsion spring. Since the torsion spring can deform and store elastic potential energy, the torque applied by the output shaft to the second rotating platform is lag-dependent when transmitted to the first rotating platform via the torsion spring. When the second rotating platform starts to rotate, its speed is greater than that of the first rotating platform, and the torsion spring deforms and stores elastic potential energy. When the speed of the first rotating platform reaches that of the second rotating platform, the torsion spring, which stores elastic potential energy, releases its elastic potential energy, which can increase the speed of the first rotating platform, thereby increasing the explosive force of the first rotating platform. Alternatively, when the motor suddenly stops rotating, the second rotating platform also stops rotating. At this time, the torsion spring, which stores elastic potential energy, will continue to drive the first rotating platform to rotate and perform work, thus increasing the explosive force.The robotic arm provided by this invention, employing the aforementioned flexible joint, has a first rotating platform mounted on its frame, capable of rotating around a predetermined axis; a motor mounted on the frame, the motor having a rotatable output shaft rotating around the predetermined axis; a second rotating platform mounted on the output shaft, which, when rotated, drives the second rotating platform to rotate around the predetermined axis; the first and second rotating platforms are spaced apart, and a torsion spring is positioned between them, with its first end engaged in a first slot on the first rotating platform and its second end engaged in a second slot on the second rotating platform. The first and second slots are spaced apart from the predetermined axis. When the motor drives the second rotating platform to rotate via the output shaft, the torque generated by the second rotating platform is transmitted to the first rotating platform via the torsion spring. The slot drives the first rotating platform to rotate. Power is transmitted between the first and second rotating platforms via a torsion spring. Since the torsion spring can deform and store elastic potential energy, the torque applied by the output shaft to the second rotating platform is lag-dependent when transmitted to the first rotating platform via the torsion spring. When the second rotating platform starts to rotate, its speed is greater than that of the first rotating platform, causing the torsion spring to deform and store elastic potential energy. When the speed of the first rotating platform reaches that of the second rotating platform, the torsion spring, which stores elastic potential energy, releases this energy to increase the speed of the first rotating platform, thereby increasing its explosive force. Alternatively, if the motor suddenly stops rotating, the second rotating platform also stops rotating. In this case, the torsion spring, which stores elastic potential energy, continues to drive the first rotating platform to rotate and perform work, further increasing its explosive force. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A three-dimensional schematic diagram of a flexible joint provided in an embodiment of the present invention;

[0019] Figure 2 A three-dimensional assembly diagram of the motor, the second rotating platform, and the torsion spring provided for an embodiment of the present invention;

[0020] Figure 3 This is a three-dimensional assembly diagram of the first rotating platform and the torsion spring provided in an embodiment of the present invention.

[0021] The following are the labeling elements in the figure:

[0022] 1-First rotating platform; 11-First slot; 12-First boss; 13-Second boss; 14-Rod body; 2-Second rotating platform; 21-Second slot; 22-Third boss; 23-Fourth boss; 231-Limiting strip; 232-Positioning strip; 3-Torsion spring; 31-First end; 32-Second end; 4-Motor. Detailed Implementation

[0023] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0024] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as being "connected to" another component, it can be directly connected to or indirectly connected to that other component.

[0025] It should be noted that, in the description of the embodiments of this application, unless otherwise stated, " / " means "or". For example, A / B can mean A or B. The "and / or" in this document is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Here, A and B can be singular or plural, respectively.

[0026] It should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention.

[0027] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0028] Please refer to the following: Figures 1 to 3The flexible joint provided by the present invention will now be described. The flexible joint includes: a frame, a first rotating platform 1 rotatably mounted on the frame about a predetermined axis, a motor 4 mounted on the frame and having an output shaft, a second rotating platform 2 mounted on the output shaft, and a torsion spring 3; the output shaft rotates about the predetermined axis; the first rotating platform 1 and the second rotating platform 2 are spaced apart in the extension direction of the predetermined axis, and the torsion spring 3 is disposed between the first rotating platform 1 and the second rotating platform 2; the first rotating platform 1 has a first slot 11, and the second rotating platform 2 has a second slot 21; the first slot 11 and the second slot 21 are spaced apart from the predetermined axis; the first end 31 of the torsion spring 3 is engaged in the first slot 11, and the second end 32 of the torsion spring 3 is engaged in the second slot 21.

[0029] Thus, a first rotating platform 1 is provided on the frame, which can rotate around a predetermined axis; a motor 4 is provided on the frame, which has an output shaft that can rotate around the predetermined axis; a second rotating platform 2 is provided on the output shaft, and when the output shaft rotates, it drives the second rotating platform 2 to rotate around the predetermined axis; the first rotating platform 1 and the second rotating platform 2 are spaced apart, and a torsion spring 3 is provided between the first rotating platform 1 and the second rotating platform 2. The first end 31 of the torsion spring 3 is engaged in the first slot 11 on the first rotating platform 1, and the second end 32 of the torsion spring 3 is engaged in the second slot 21 on the second rotating platform 2. The first slot 11 and the second slot 21 are spaced apart from the predetermined axis (so that when the first end 31 of the torsion spring 3 applies a pushing force to the inner wall of the first slot 11 (the direction of the pushing force is towards the circumferential direction of the predetermined axis) (the circumferential direction of the predetermined axis is the direction around the predetermined axis), it drives the first rotating platform 1 to rotate). The motor 4 drives the second rotating platform 2 to rotate through the output shaft. When platform 2 rotates, the torque generated by the second rotating platform 2 is transmitted to the first slot 11 on the first rotating platform 1 through the torsion spring 3, which drives the first rotating platform 1 to rotate. The first rotating platform 1 and the second rotating platform 2 need to transmit power through the torsion spring 3. Since the torsion spring 3 can deform and store elastic potential energy, the torque applied by the output shaft to the second rotating platform 2 is lag-dependent when transmitted to the first rotating platform 1 through the torsion spring 3. When the second rotating platform 2 just starts to rotate, the rotation speed of the second rotating platform 2 is greater than that of the first rotating platform 1. The torsion spring 3 deforms and stores elastic potential energy. When the rotation speed of the first rotating platform 1 reaches the rotation speed of the second rotating platform 2, the torsion spring 3, which stores elastic potential energy, releases its elastic potential energy, which can increase the rotation speed of the first rotating platform 1, thereby increasing the explosive force of the first rotating platform 1. Or when the motor 4 suddenly stops rotating, the second rotating platform 2 also stops rotating. At this time, the torsion spring 3 stores elastic potential energy and will continue to drive the first rotating platform 1 to rotate and do work, increasing the explosive force.

[0030] In one embodiment, the middle section of the torsion spring 3 is a columnar spring portion, the first end 31 of the torsion spring 3 is connected to one end of the columnar spring portion, and the second end 32 of the torsion spring 3 is connected to the other end of the columnar spring portion.

[0031] In one embodiment, a shaft coaxial with a predetermined axis is provided on the first rotating stage 1 or the second rotating stage 2, and a torsion spring 3 is sleeved on the shaft. In this way, the shaft positions the torsion spring 3.

[0032] In one embodiment, the first end 31 of the torsion spring 3 is engaged and fixed in the first slot 11 on the first rotating platform 1, and the second end 32 of the torsion spring 3 is engaged and fixed in the second slot 21 on the second rotating platform 2.

[0033] In one embodiment, the maximum angle at which the first end 31 and the second end 32 of the torsion spring 3 can rotate relative to each other about a predetermined axis is forty-five degrees. In one embodiment, in the initial state, the first end 31 and the second end 32 of the torsion spring 3 are perpendicular to each other.

[0034] In one embodiment, the predetermined axis is a straight line.

[0035] In one embodiment, the flexible joint is a SEA joint. SEA is defined as: Series Elastic Actuator. Regarding the "elasticity" in the above concept: Actuator units that achieve force feedback at the mechanical level (excluding current loops) all utilize the deformation and elasticity of materials to measure torque or force. This can be understood as having "elasticity" from a macroscopic or microscopic perspective, and thus falls under the category of SEA.

[0036] Further, please refer to Figures 1 to 3 As a specific embodiment of the flexible joint provided by the present invention, in the circumferential direction surrounding the predetermined axis, the two side walls of the first slot 11 are respectively located on the movement path of the first end 31 of the torsion spring 3 rotating around the predetermined axis. Thus, when the first end 31 of the torsion spring 3 moves in one direction around the predetermined axis, it will be blocked by one side wall of the first slot 11; when the first end 31 of the torsion spring 3 moves in another direction around the predetermined axis, it will be blocked by the other side wall of the first slot 11, thereby improving the positional stability of the first end 31 of the torsion spring 3 relative to the first rotating platform 1.

[0037] Further, please refer to Figures 1 to 3 As a specific embodiment of the flexible joint provided by the present invention, in the circumferential direction surrounding the predetermined axis, the two side walls of the second slot 21 are respectively located on the movement path of the second end 32 of the torsion spring 3 rotating around the predetermined axis. Thus, when the second end 32 of the torsion spring 3 moves in one direction around the predetermined axis, it will be blocked by one side wall of the second slot 21; when the second end 32 of the torsion spring 3 moves in another direction around the predetermined axis, it will be blocked by the other side wall of the second slot 21, thereby improving the positional stability of the second end 32 of the torsion spring 3 relative to the second rotating platform 2.

[0038] Further, please refer to Figures 1 to 3 As a specific embodiment of the flexible joint provided by the present invention, a first boss 12 and a second boss 13 are protruding on the inner wall of the first rotating platform 1 facing the second rotating platform 2, and a first groove 11 is formed between the first boss 12 and the second boss 13. In this way, the first end 31 of the torsion spring 3 is restricted between the first boss 12 and the second boss 13, which facilitates the stability of the relative position of the first end 31 of the torsion spring 3 with the first rotating platform 1.

[0039] Further, please refer to Figures 1 to 3 In one specific embodiment of the flexible joint provided by the present invention, the first boss 12 is cylindrical, and / or the second boss 13 is cylindrical. This facilitates processing.

[0040] Further, please refer to Figures 1 to 3 As a specific embodiment of the flexible joint provided by the present invention, a third protrusion 22 and a fourth protrusion 23 are provided on the inner wall of the second rotating platform 2 facing the first rotating platform 1, and a second groove 21 is formed between the third protrusion 22 and the fourth protrusion 23. In this way, the second end 32 of the torsion spring 3 is restricted between the third protrusion 22 and the fourth protrusion 23, which facilitates the stability of the relative position of the second end 32 of the torsion spring 3 with the second rotating platform 2.

[0041] Further, please refer to Figures 1 to 3 In one specific embodiment of the flexible joint provided by the present invention, the third boss 22 is cylindrical, and / or the fourth boss 23 is cylindrical. This facilitates processing.

[0042] In one embodiment, a rod 14 is provided on the first rotating platform 1, with the predetermined axis being the axis of the rod 14; a torsion spring 3 is sleeved on the rod 14. Thus, the torsion spring 3 can be positioned by being sleeved on the rod 14.

[0043] In one embodiment, a positioning hole is provided on the frame, and the rod 14 is inserted into the positioning hole. In this way, the rod 14 can rotate around a predetermined axis when it rotates in the positioning hole.

[0044] In one embodiment, the second rotary table 2 is detachably fixed to the output shaft. This facilitates the fixing and separation of the second rotary table 2 and the output shaft.

[0045] Further, please refer to Figures 1 to 3As a specific embodiment of the flexible joint provided by the present invention, the fourth boss 23 includes: a limiting strip 231 and a positioning strip 232 located outside the predetermined axis and extending in the circumferential direction along the predetermined axis; the extension direction of the limiting strip 231 is perpendicular to the predetermined axis, and the limiting strip 231 and the predetermined axis are spaced apart; one end of the limiting strip 231 is fixedly connected to one end of the positioning strip 232, and a U-shaped cavity is formed between the limiting strip 231 and the positioning strip 232; the second end of the torsion spring 3 is clamped between the limiting strip 231 and the third boss; the extension path of the torsion spring 3 from the second end to the first end gradually moves away from the second rotating platform 2, and in the axial direction of the predetermined axis, the first end of the torsion spring 3 is located outside the limiting strip 231. Thus, the limiting strip 231 and the positioning strip 232 are connected together to form the fourth boss 23, with one end of the limiting strip 231 fixedly connected to one end of the positioning strip 232; the second end of the torsion spring 3 is clamped between the limiting strip 231 and the third boss, and the positioning strip 232 extends in the circumferential direction along the predetermined axis. When the second end of the torsion spring 3 transmits pressure to the positioning strip 232 through the limiting strip 231, the stress on the positioning strip 232 can be released in the circumferential direction along the predetermined axis, reducing the deformation in the radial direction of the predetermined axis; A U-shaped cavity is formed between the limiting strip 231 and the positioning strip 232, which facilitates stress release when stress is transmitted between the limiting strip 231 and the positioning strip 232. Since the positioning strip 232 extends circumferentially along a predetermined axis, gaps are formed at both ends of the positioning strip 232, and the connection between the limiting strip 231 and the positioning strip 232 is located within these gaps. This allows some stress on the limiting strip 231 to be directly transmitted to one end of the positioning strip 232, while the other part of the limiting strip 231... The stress can be transmitted to the other end of the positioning strip 232 through the second rotating platform 2; the positioning strip 232 extends in the circumferential direction along the predetermined axis, which facilitates the release of stress along the position around the predetermined axis; the extension direction of the limiting strip 231 is set perpendicular to the predetermined axis, and the limiting strip 231 is spaced apart from the predetermined axis to reduce the deformation at the predetermined axis caused by the deformation of the limiting strip 231; the extension path of the torsion spring 3 from the second end to the first end gradually moves away from the second rotating platform 2, and in the axial direction of the predetermined axis, the first end of the torsion spring 3 is located outside the limiting strip 231, so that the torsion spring 3 is less likely to generate a thrust on the second rotating platform 2 in the direction of the predetermined axis during the torsion process. As the torsion spring 3 moves away from the second rotating platform 2, it gradually passes over the positioning strip 232, that is, the stress transmitted along the torsion spring 3 will be transmitted and pass over the positioning strip 232, so that the deformation of the torsion spring 3 is not restricted by the positioning strip 232, and also to prevent the torsion spring 3 from hitting the positioning strip 232 during the expansion or contraction process after passing over the positioning strip 232. In one embodiment, the torsion spring 3 extends to the outside of the positioning strip 232 in a helical structure.

[0046] Further, please refer to Figures 1 to 3As a specific embodiment of the flexible joint provided by the present invention, a gap is formed between the two ends of the positioning strip 232 in the circumferential direction of the predetermined axis, and one end of the limiting strip 231 connected to the positioning strip 232 is located within the gap. Thus, the positioning strip 232 extends along the circumferential direction of the predetermined axis, and the stress on the positioning strip 232 can be released along the circumferential direction of the predetermined axis. Notches are formed at both ends of the positioning strip 232 to prevent the stress at both ends of the positioning strip 232 from contacting and transmitting to each other; that is, the stress of the positioning strip 232 can be transmitted through its own extension direction, and the stress of the positioning strip 232 can also be transmitted along the surface of the second rotating platform 2. One end of the limiting strip 231 is located within the gap, so that the stress applied to the limiting strip 231 by the torsion spring 3 can be transmitted along the positioning strip 232. Since the two ends of the positioning strip 232 easily maintain the same frequency of vibration, the limiting strip 231 located within the gap easily maintains its own position stability under the influence of the positioning strip 232 on both sides, which easily maintains the same frequency of vibration.

[0047] Please see Figures 1 to 3The present invention also provides a robotic arm, including: flexible joints. Thus, the arms of the robotic arm can be connected via flexible joints. Due to the use of the aforementioned flexible joints, a first rotating platform 1 is provided on the frame, which can rotate around a predetermined axis; a motor 4 is provided on the frame, the motor 4 having a rotatable output shaft that rotates around the predetermined axis; a second rotating platform 2 is provided on the output shaft, and when the output shaft rotates, it drives the second rotating platform 2 to rotate around the predetermined axis; the first rotating platform 1 and the second rotating platform 2 are spaced apart, and a torsion spring 3 is provided between the first rotating platform 1 and the second rotating platform 2. The first end 31 of the torsion spring 3 is engaged in a first slot 11 on the first rotating platform 1, and the second end 32 of the torsion spring 3 is engaged in a second slot 21 on the second rotating platform 2. The first slot 11 and the second slot 21 are spaced apart from the predetermined axis (thus, when the first end 31 of the torsion spring 3 applies a pushing force to the inner wall of the first slot 11 (the direction of the pushing force: circumferential direction towards the predetermined axis), it drives the first rotating platform 1 to rotate). The motor 4 drives the first rotating platform 1 to rotate via the output shaft. When the second rotating platform 2 rotates, the torque generated by the second rotating platform 2 is transmitted to the first slot 11 on the first rotating platform 1 through the torsion spring 3, which drives the first rotating platform 1 to rotate. The first rotating platform 1 and the second rotating platform 2 need to transmit power through the torsion spring 3. Since the torsion spring 3 can deform and store elastic potential energy, the torque applied by the output shaft to the second rotating platform 2 is lag-dependent when transmitted to the first rotating platform 1 through the torsion spring 3. When the second rotating platform 2 starts to rotate, the rotation speed of the second rotating platform 2 is greater than that of the first rotating platform 1. The torsion spring 3 deforms and stores elastic potential energy. When the rotation speed of the first rotating platform 1 reaches the rotation speed of the second rotating platform 2, the torsion spring 3, which stores elastic potential energy, releases its elastic potential energy, which can increase the rotation speed of the first rotating platform 1, thereby increasing the explosive force of the first rotating platform 1. Or when the motor 4 suddenly stops rotating, the second rotating platform 2 also stops rotating. At this time, the torsion spring 3 stores elastic potential energy and will continue to drive the first rotating platform 1 to rotate and do work, increasing the explosive force.

[0048] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and substitutions can be made without departing from the technical principles of the present invention, and these improvements and substitutions should also be considered within the scope of protection of the present invention.

Claims

1. A flexible joint, characterized in that, include: The frame includes a frame, a first rotating platform (1) rotatably mounted on the frame about a predetermined axis, a motor (4) mounted on the frame and having an output shaft, a second rotating platform (2) mounted on the output shaft, and a torsion spring (3); the output shaft rotates about the predetermined axis; the first rotating platform (1) and the second rotating platform (2) are spaced apart in the extension direction of the predetermined axis, the torsion spring (3) is disposed between the first rotating platform (1) and the second rotating platform (2), the first rotating platform (1) has a first slot (11), and the second rotating platform (4) has a first slot (11). 2) A second slot (21) is provided on the upper part, and the first slot (11) and the second slot (21) are respectively spaced apart from the predetermined axis. The first end (31) of the torsion spring (3) is engaged in the first slot (11), and the second end (32) of the torsion spring (3) is engaged in the second slot (21). A third protrusion (22) and a fourth protrusion (23) are provided on the inner wall of the second rotating platform (2) facing the first rotating platform (1), and the second slot (21) is formed between the third protrusion (22) and the fourth protrusion (23). The fourth boss (23) includes: a limiting strip (231) and a positioning strip (232) located outside the predetermined axis and extending in the circumferential direction of the predetermined axis; the extension direction of the limiting strip (231) is perpendicular to the predetermined axis, and the limiting strip (231) and the predetermined axis are spaced apart; one end of the limiting strip (231) is fixedly connected to one end of the positioning strip (232), and a U-shaped cavity is formed between the limiting strip (231) and the positioning strip (232); the second end (32) of the torsion spring (3) is clamped between the limiting strip (231) and the third boss; the extension path of the torsion spring (3) from the second end (32) to the first end (31) gradually moves away from the second rotating platform (2), and in the axial direction of the predetermined axis, the first end (31) of the torsion spring (3) is located outside the limiting strip (231).

2. The flexible joint as described in claim 1, characterized in that, In the circumferential direction surrounding the predetermined axis, the two side walls of the first slot (11) are respectively located on the movement path of the first end (31) of the torsion spring (3) rotating around the predetermined axis.

3. The flexible joint as described in claim 1, characterized in that, In the circumferential direction surrounding the predetermined axis, the two side walls of the second slot (21) are respectively located on the movement path of the second end (32) of the torsion spring (3) rotating around the predetermined axis.

4. The flexible joint according to any one of claims 1 to 3, characterized in that, The first rotating platform (1) has a first protrusion (12) and a second protrusion (13) protruding on the inner wall facing the second rotating platform (2), and the first slot (11) is formed between the first protrusion (12) and the second protrusion (13).

5. The flexible joint as described in claim 4, characterized in that, The first boss (12) is cylindrical, and / or the second boss (13) is cylindrical.

6. The flexible joint as described in claim 1, characterized in that, The third boss (22) is cylindrical, and / or the fourth boss (23) is cylindrical.

7. The flexible joint according to any one of claims 1 to 3, characterized in that, A rod (14) is provided on the first rotating platform (1), and the predetermined axis is the axis of the rod (14); the torsion spring (3) is sleeved on the rod (14).

8. The flexible joint as described in claim 7, characterized in that, The frame is provided with positioning holes, and the rod (14) is inserted into the positioning holes.

9. A robotic arm, characterized in that, include: The flexible joint as described in any one of claims 1 to 8.

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