Limiting structure and mechanical arm applied in limited space

Abstract

The utility model provides a kind of limiting structure and manipulator applied in limited space, comprising: step surface, it is configured as the first part of installation rotating support element and be located on the outer wall of shaft along circumference;Limiting groove, corresponding step surface is located on the outer wall of shaft along circumference;Limiting piece, it is elastic and elastic abuts between the groove wall of limiting groove and the end face of first part, and with the local part of step surface forms the clamping space of axial elastic self-adapting to clamp first part;The abutting force of limiting piece to limiting groove is used to limit the axial and radial position of limiting piece relative to shaft, and the elastic restoring force of limiting piece is used to act on first part in pre-tightening state to limit the axial position of first part relative to shaft, so that first part is kept fixed relative to shaft.The utility model can realize the reliable limiting of bearing without using traditional space-occupying limiting component and without reducing the diameter of shaft, to meet the requirement of compact structure of limited space and the strength and carrying capacity requirement of shaft simultaneously.

Description

Technical Field

[0001] This utility model relates to the field of semiconductor manufacturing equipment technology, and in particular to a limiting structure and a robotic arm used in a limited space. Background Technology

[0002] In mechanical transmission and structural design, bearings are the core components for achieving low-friction engagement between relatively rotating parts, and their installation stability directly affects the overall operating accuracy and reliability of the equipment.

[0003] For axial positioning of the inner ring of a bearing, the shoulder + pressure plate method is a widely used solution in existing technology: a shoulder is machined on the shaft as a preliminary positioning of the inner ring of the bearing, and then a flange pressure plate (usually a ring or semi-ring structure) is used to cover the end face of the inner ring of the bearing. The pressure plate is fixed to the shaft end or housing with bolts, thereby pressing the inner and outer rings of the bearing together and restricting their axial movement. Due to its high structural stability, this method is widely used in conventional space scenarios such as machine tools and automotive transmissions.

[0004] However, the shortcomings of traditional limiting methods are particularly prominent in devices such as robotic arms that have strict requirements for space, weight, and flexibility; the joints of robotic arms need to integrate multiple modules such as drive, transmission, and sensing, and the internal space is highly compact.

[0005] Using a pressure plate would occupy valuable axial or radial space, resulting in increased joint size and reduced flexibility. In addition, the extra parts would increase the overall weight and affect dynamic response performance.

[0006] If no additional axial or radial space is added, some designs will compress the size by reducing the shaft diameter or shortening the shaft shoulder length to alleviate space pressure. However, this will directly lead to a decrease in the shaft's load-bearing capacity. Reducing the shaft diameter will decrease the shaft's bending and load-bearing capacity.

[0007] Therefore, there is an urgent need for a bearing limiting solution that does not rely on traditional pressure plates and other components, occupies less space, and has a simpler structure, in order to meet the high-precision and high-reliability transmission requirements in limited space. Utility Model Content

[0008] The purpose of this utility model is to provide a limiting structure and manipulator for use in a limited space, which can achieve reliable bearing limiting without using traditional space-consuming limiting components and without reducing the shaft diameter, so as to simultaneously meet the requirements of structural compactness in a limited space and the requirements of shaft strength and load-bearing capacity.

[0009] This utility model provides a limiting structure for use in a confined space, the confined space being formed within a robotic arm. The robotic arm includes at least one arm body, each arm body comprising a shaft and a rotary support element sleeved and mounted on the shaft. The limiting structure includes: A stepped surface is provided circumferentially on the outer wall of the shaft and configured as the first part for mounting the rotary support element; A limiting groove is provided on the outer wall of the shaft along the circumferential direction corresponding to the stepped surface; The limiting member is elastic and elastically abuts against the groove wall of the limiting groove and the end face of the first part, forming an axially elastically adaptive clamping space with a part of the stepped surface to clamp the first part. The limiting member abuts against the limiting groove to limit the axial and radial positions of the limiting member relative to the shaft. The elastic restoring force of the limiting member acts on the first part in a pre-tightened state to limit the axial position of the first part relative to the shaft, thereby keeping the first part fixed relative to the shaft.

[0010] In one possible embodiment, the limiting member has an inner edge that extends radially inward into the limiting groove, the inner edge abutting against the groove wall of the limiting groove.

[0011] In one possible embodiment, the limiting member has an outer edge that protrudes radially outward from the limiting groove, the outer edge abutting against the end face of the first portion. In one possible embodiment, the limiting member is formed by spirally winding a strip-shaped plate around the central axis in a corrugated manner to form a spiral coil with more than one turn, and the spiral coil has partially overlapping areas along the axial projection direction of the central axis, forming peaks and troughs. In one possible embodiment, the limiting member is open-loop shaped, having a first end, a second end, and a spiral body connecting the first end and the second end with at least one turn. In one possible embodiment, the limiting groove has a first wall disposed opposite to the opening of the limiting groove, and the inner circumferential surface of the limiting member abuts against the first wall to limit the radial displacement of the limiting member relative to the shaft. In one possible embodiment, the limiting groove has a second wall connected to the opening of the limiting groove and disposed opposite to the first part. The elastic restoring force of the limiting member abuts against the end face of the second wall and the first part in a pre-tightened state to limit the axial displacement of the first part relative to the shaft.

[0012] In one possible embodiment, the limiting groove has a second wall connected to the opening of the limiting groove and disposed opposite to the first portion, and the axial deformation of the limiting member is greater than the distance between the second wall and the end face of the first portion. In one possible embodiment, the limiting member has a first state in which no axial force is applied and a second state in which an axial force is applied. During the transition from the first state to the second state, the area covered by the radial projection of the limiting member either increases or remains unchanged. In one possible embodiment, the limiting member has at least one abutment point that abuts against a local point on the end face of the first portion in a point-contact manner; or, The limiting member has at least one abutting surface, which abuts against a partial or complete area of ​​the first partial end face in a surface contact manner; or, The limiting member has at least one abutment point and at least one abutment surface. The abutment point abuts against a local point on the first partial end face in a point-contact manner, and the abutment surface abuts against a local area on the first partial end face in a surface-contact manner; or... The limiting member has at least one abutment point, and each abutment point is integrally formed with the limiting member body; or... The limiting member has at least one abutting surface, and each abutting surface is integrally formed with the limiting member body; or... The limiting member has at least one abutment point and at least one abutment surface, and each abutment point and each abutment surface is integrally formed with the limiting member body; or... The limiting member has at least one abutment point, and the projections of each abutment point along the axial direction are dispersed or uniformly distributed on the end face of the first part; or, The limiting member has at least one abutting surface, and the projections of each abutting surface along the axial direction are dispersed or uniformly distributed on the end face of the first part; or, The limiting member has at least one contact point and at least one contact surface, and the projections of each contact point and each contact surface along the axial direction are dispersed or uniformly distributed on the end face of the first part.

[0013] This utility model also provides a robotic arm, including: a robotic arm body, at least one arm body and an end effector assembly, wherein at least one of the arm bodies is provided with a shaft, a rotary support element, a pulley, and a limiting structure as described in any of the above embodiments for use in a limited space, wherein the pulley is sleeved and fixed to a second part of the rotary support element, and the second part is rotatable relative to the first part.

[0014] The beneficial effects of the limiting structure provided by this utility model, applied in a confined space, are as follows: On the one hand, the abutment force of the limiting member against the limiting groove is used to limit the axial and radial positions of the limiting member relative to the shaft. The elastic restoring force of the limiting member acts on the first part in a pre-tightened state to limit the axial position of the first part relative to the shaft, thereby keeping the first part fixed relative to the shaft. On the other hand, the traditional axial extension component of the pressure plate is eliminated, eliminating the need to reserve space for pressure plate installation or bolt connection areas, significantly reducing the axial dimension of the limiting structure, meeting the requirement of structural compactness in a confined space, and ensuring the load-bearing capacity of the shaft. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the limiting structure, shaft, rotary support element and pulley of this utility model applied in a limited space.

[0016] Figure 2 This is a schematic diagram of the limiting structure of this utility model applied in a limited space.

[0017] Figure 3 This is a schematic diagram of the limiting component in a limiting structure within a confined space, which is an application of this utility model.

[0018] Figure 4 This is a schematic diagram of the robotic arm of this utility model.

[0019] Explanation of reference numerals in the attached drawings: 100, limiting structure; 110, stepped surface; 111, first section; 112, second section; 120, limiting groove; 121, groove opening; 122, first wall; 123, second wall; 124, third wall; 130, limiting element; 131, inner edge; 132, outer edge; 133, crest; 134, trough; 135, first end; 136, second end; 137, inner circumferential surface; 200, robot body; 301, upper arm; 302, forearm; 310, shaft; 320, rotary support element; 321, first part; 322, second part; 323, rolling element; 330, pulley; A, shoulder joint axis; B, elbow joint axis; C, wrist joint axis; 400, end effector assembly; 410, end effector. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0021] To address the problems existing in the prior art, embodiments of this utility model provide a limiting structure applied within a confined space. The confined space is formed within a robotic arm, which includes at least one arm body. The arm body includes a shaft 310 and a rotary support element 320 sleeved and mounted on the shaft 310. See [link to previous section]. Figure 1 and Figure 2 The limiting structure 100 includes a stepped surface 110, a limiting groove 120, and a limiting member 130. The stepped surface 110 is circumferentially disposed on the outer wall of the shaft 310 and configured to mount a first portion 321 of the rotating support element 320. The limiting groove 120 is circumferentially disposed on the outer wall of the shaft 310 corresponding to the stepped surface 110. The limiting member 130 is elastic and elastically abuts against the groove wall of the limiting groove 120 and the end face of the first portion 321. The limiting member 130 and the stepped surface 110 partially form an axially elastically adaptive clamping space to clamp the first portion 321. The abutting force of the limiting member 130 against the limiting groove 120 is used to limit the axial and radial positions of the limiting member 130 relative to the shaft 310. The elastic restoring force of the limiting member 130 acts on the first portion 321 in a pre-tightened state to limit the axial position of the first portion 321 relative to the shaft 310, thereby keeping the first portion 321 fixed relative to the shaft 310.

[0022] In this embodiment, an axial, controllable, adaptive, floating, and elastic clamping space is formed by the step surface 110 and the limiting member 130. On the one hand, the limiting member 130 is tightly abutted between the groove wall of the limiting groove 120 and the end face of the first part 321 of the rotating support element 320 through elastic deformation. Its abutting force ensures the precise positioning of the limiting member 130 relative to the shaft 310 and restricts the displacement of the limiting member 130 in the axial and radial directions. On the other hand, the elastic restoring force of the limiting member 130 continues to act on the first part 321 of the rotating support element 320, forming an axial constraint force in the pre-tightened state, which restricts the first part 321 of the rotating support element 320 from rotating relative to the shaft 310.

[0023] Furthermore, by forming a stepped surface 110 along the circumferential direction on the outer wall of the shaft 310 to install the first part 321 of the rotating support element 320, and by forming a limiting groove 120 along the circumferential direction on the outer wall of the shaft 310 to install the elastic limiting member 130, the embedded installation structure design reduces the axial and radial space occupation, meeting the requirement of structural compactness in limited space, and is particularly suitable for scenarios with limited internal space such as robotic arm joints. Moreover, it does not rely on traditional shaft shoulders, pressure plates, or other components, nor does it require reducing the shaft diameter, thus ensuring the load-bearing capacity of the shaft 310.

[0024] In summary, compared to traditional solutions, the limiting structure 100 in this embodiment does not require additional components such as flange plates, avoiding axial or radial space occupation caused by plate installation. This allows the robotic joint to achieve the same function within a more compact space, while also reducing overall weight. Since there is no need to compress the shaft diameter or shorten the shaft shoulder to accommodate the plate, the load-bearing capacity of the shaft 310 is ensured.

[0025] The specific structure of the limiting groove 120 will be explained in detail below.

[0026] In one embodiment, see Figure 2 The limiting groove 120 has a first wall 122 disposed opposite to the opening 121 of the limiting groove 120, and the first wall 122 has an axial height and an outer peripheral surface. The limiting groove 120 has a second wall 123 connected to the opening 121 of the limiting groove 120 and disposed opposite to the first part 321, and a third wall 124 connected to the opening 121 of the limiting groove 120 and disposed opposite to the second wall 123. The second wall 123 and the third wall 124 form a predetermined fixed axial distance along the axial direction of the shaft 310.

[0027] In one specific embodiment, see Figure 2 The stepped surface 110 includes a first segment 111 and a second segment 112 vertically connected to the first segment 111. The end of the first segment 111 away from the second segment 112 is connected to the third wall 124 of the limiting groove 120.

[0028] The specific structure and configuration of the limiting component 130 will be explained in detail below.

[0029] In one embodiment, see Figure 1 and Figure 3 The limiting member 130 has an inner edge 131 that extends radially inward into the limiting groove 120, and the inner edge 131 abuts against the groove wall of the limiting groove 120. Specifically, the inner peripheral surface 137 of the inner edge 131 surrounds and abuts against the groove wall of the limiting groove 120. In this embodiment, the inner edge 131 extends radially inward into the limiting groove 120, and its inner peripheral surface 137 surrounds and abuts against the groove wall of the limiting groove 120 to limit the axial and radial displacement of the limiting member 130 relative to the shaft 310.

[0030] In another embodiment, see Figure 1 and Figure 3The limiting member 130 has an outer edge 132 that protrudes radially outward from the limiting groove 120 and abuts against the end face of the first portion 321. In this embodiment, the limiting member 130 is maintained in the abutting state by its own elasticity. The inner edge 131 abuts against the groove wall of the limiting groove 120, and the outer edge 132 abuts against the end face of the first portion 321 and acts on the first portion 321 in a pre-tightened state to limit the axial displacement of the first portion 321 relative to the shaft 310, thereby keeping the first portion 321 fixed relative to the shaft 310.

[0031] In one specific embodiment, see Figure 3 The limiting member 130 is formed by spirally winding a strip-shaped plate around its central axis in a corrugated manner, creating more than one spiral coil. The spiral coils partially overlap in the axial projection direction along the central axis, forming crests 133 and troughs 134. In this embodiment, the corrugated spiral structure provides stronger elastic force to limit the axial displacement of the first portion 321 of the rotating support element 320. The corrugations also provide additional deformation buffering in the radial and localized areas, enabling the limiting member 130 to maintain a linear elastic response over a large load range, thus avoiding stress concentration and fatigue failure problems that are common with rigid limiting members 130.

[0032] In another specific embodiment, see Figure 3 The limiting member 130 is an open ring shape, having a first end 135, a second end 136, and at least one spiral ring connecting the first end 135 and the second end 136. In this embodiment, the open ring structure enables the limiting member 130 to have the ability to open and close radially. During installation, the limiting member 130 can be fitted onto the shaft 310 through appropriate radial expansion, and then automatically closes and tightens onto the shaft 310 using its elastic recovery characteristics, making it suitable for complex assembly environments with limited space. The opening gap between the first end 135 and the second end 136 creates space for radial elastic deformation. When the limiting member 130 is installed in place, the open ring structure generates an inwardly contracting radial preload, ensuring a tight fit between the inner edge 131 and the groove wall of the limiting groove 120, achieving a durable and stable axial and radial limiting effect. In one embodiment, see Figure 1 , Figure 2 and Figure 3 The inner circumferential surface 137 of the limiting member 130 abuts against the first wall 122 to limit the radial displacement of the limiting member 130 relative to the shaft 310. In this embodiment, the inner circumferential surface 137 of the limiting member 130 surrounds and abuts against the first wall 122 of the limiting groove 120, constraining the axial degree of freedom of the limiting member 130 and playing an axial limiting role. In another embodiment, see Figure 1 , Figure 2 and Figure 3The elastic restoring force of the limiting member 130 ensures that it is in a pre-tightened state abutting against the end face of the second wall 123 and the first part 321, thereby limiting the axial displacement of the first part 321 relative to the shaft 310. In this embodiment, the elastic restoring force of the limiting member 130 ensures that the limiting member 130 is always in a pre-tightened state abutting against the end face of the second wall 123 and the first part 321 of the limiting groove 120, thereby achieving axial positional constraint on the first part 321 of the rotary support element 320 and avoiding the axial movement problem existing in traditional clearance fits.

[0033] In yet another embodiment, see Figure 1 and Figure 2 The axial deformation of the limiting member 130 is greater than the distance between the end face of the second wall 123 and the first part 321, ensuring that the limiting member 130 is in a compressed pre-tightened state after assembly, eliminating the loosening or poor contact problems that may occur during assembly, and achieving effective and stable axial constraint force. In one specific embodiment, see Figure 1 and Figure 2 The limiting member 130 has a first state without axial force and a second state with axial force applied. The limiting member 130 progressively wraps radially inward around the first wall 122. The spiral coil is limited by a fixed distance between the second wall 123 and the end face of the first portion 321. During the transition from the first state to the second state, the area covered by the radial projection of the limiting member 130 either increases or remains unchanged. In this embodiment, when the limiting member 130 transitions from the first state to the second state, the expansion of the radial projection range increases the contact area between the limiting member 130 and the groove wall of the limiting groove 120 and / or the end face of the first portion 321, thereby enhancing the axial constraint force on the first portion 321.

[0034] In some possible embodiments, see Figure 1 The limiting member 130 has at least one abutment point, which abuts against a partial point on the end face of the first portion 321 in a point-contact manner; or, the limiting member 130 has at least one abutment surface, which abuts against a partial or all area of ​​the end face of the first portion 321 in a surface-contact manner; or, the limiting member 130 has at least one abutment point and at least one abutment surface, where the abutment point abuts against a partial point on the end face of the first portion 321 in a point-contact manner, and the abutment surface abuts against a partial area of ​​the end face of the first portion 321 in a surface-contact manner. In these embodiments, point-contact abutment is achieved by the abutment point of the limiting member 130 and a partial point on the end face of the first portion 321; and / or, surface-contact abutment is achieved by the abutment surface of the limiting member 130 and a partial or all area of ​​the end face of the first portion 321. The configuration can be flexibly adjusted according to process requirements to meet different axial and radial limiting needs.

[0035] In some possible embodiments, see Figure 1 and Figure 3 The limiting member 130 has at least one abutment point, and each abutment point is integrally formed with the body of the limiting member 130; or, the limiting member 130 has at least one abutment surface, and each abutment surface is integrally formed with the body of the limiting member 130; or, the limiting member 130 has at least one abutment point and at least one abutment surface, and each abutment point and each abutment surface is integrally formed with the body of the limiting member 130. In these embodiments, the abutment point and / or abutment surface of the limiting member 130 are integrally formed with the body of the limiting member 130, thereby enhancing the overall integrity of the structure.

[0036] In some possible embodiments, see Figure 1 and Figure 3 The limiting member 130 has at least one abutment point, and the axial projections of each abutment point are dispersed or uniformly distributed on the end face of the first part 321; or, the limiting member 130 has at least one abutment surface, and the axial projections of each abutment surface are dispersed or uniformly distributed on the end face of the first part 321; or, the limiting member 130 has at least one abutment point and at least one abutment surface, and the axial projections of each abutment point and each abutment surface are dispersed or uniformly distributed on the end face of the first part 321. In these embodiments, the dispersed distribution of the abutment points and abutment surfaces on the end face of the first part 321 ensures that the axial load can be distributed and transmitted through multiple distribution points, avoiding overload phenomena in single points or local areas. The uniform distribution ensures that the load acting on the first part 321 is evenly distributed.

[0037] In a preferred embodiment, the limiting member 130 is a wave spring.

[0038] This utility model also provides a robotic arm, see [link]. Figure 4 The robotic arm includes: a robotic arm body 200, at least one arm body and an end effector assembly 400, at least one arm body is provided with a shaft 310, a rotary support element 320, a pulley 330, and a limiting structure 100 applied in a limited space as in any of the above embodiments, the pulley 330 is sleeved and fixed to a second part 322 of the rotary support element 320, a rolling element 323 is assembled between the first part 321 and the second part 322, and the second part 322 can rotate relative to the first part 321.

[0039] In one embodiment, see Figure 1 The rotating support element 320 is a bearing, the first part 321 is the inner ring of the bearing, the second part 322 is the outer ring of the bearing, and the rolling element 323 is a roller, so that the inner ring and the outer ring can rotate relative to each other.

[0040] In one specific embodiment, see Figure 4At least one arm has at least one joint axis, such as a shoulder joint axis A, an elbow joint axis B, and a wrist joint axis C. At least one arm includes an upper arm 301 pivotally connected to the manipulator body 200 and a forearm 302 pivotally connected to the upper arm 301. The upper arm 301 is rotatable relative to the manipulator body 200 about the shoulder joint axis A, and the forearm 302 is rotatable relative to the upper arm 301 about the elbow joint axis B. An end effector assembly 400 is pivotally connected to the forearm 302 and is rotatable relative to the forearm 302 about the wrist joint axis C.

[0041] Further, see Figure 1 and Figure 4 The shaft 310 is rotatably mounted on the joint axis, and the pulley 330 is mounted on the outer wall of the shaft 310 in a manner that rotates relative to the shaft 310 with the joint axis as the center.

[0042] Specifically, see Figure 4 The end effector assembly 400 includes at least one end effector 410 that is pivotally connected to the forearm 302 and rotates independently of each other.

[0043] In the description of this utility model, it should be understood that the terms "comprising" and "having" as used herein, and any variations thereof, are intended to cover non-exclusive inclusion, for example, a process, method, system, product, or device that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such process, method, product, or device.

[0044] It should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", and "outer" 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 this utility model 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 this utility model.

[0045] 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 utility model, unless otherwise stated, "a plurality of" means two or more.

[0046] While the embodiments of this utility model have been described in detail above, it will be apparent to those skilled in the art that various modifications and variations can be made to these embodiments. However, it should be understood that such modifications and variations fall within the scope and spirit of this utility model. Furthermore, the utility model described herein may have other embodiments and can be implemented or realized in various ways. Unless otherwise defined, the technical or scientific terms used herein should have the ordinary meaning understood by one of ordinary skill in the art to which this utility model pertains.

Claims

1. A limiting structure for use in a confined space, the confined space being formed within a robotic arm, the robotic arm comprising at least one arm body, the arm body comprising a shaft (310) and a rotary support element (320) sleeved and mounted on the shaft (310), characterized in that, The limiting structure (100) includes: A stepped surface (110) is provided circumferentially on the outer wall of the shaft (310) and configured as the first part (321) for mounting the rotary support element (320). A limiting groove (120) is provided circumferentially on the outer wall of the shaft (310) corresponding to the stepped surface (110); The limiting member (130) is elastic and elastically abuts against the groove wall of the limiting groove (120) and the end face of the first part (321), forming an axially elastically adaptive clamping space with a part of the stepped surface (110) to clamp the first part (321). The limiting member (130) abuts against the limiting groove (120) to limit the axial and radial positions of the limiting member (130) relative to the shaft (310). The elastic restoring force of the limiting member (130) acts on the first part (321) in a pre-tightened state to limit the axial position of the first part (321) relative to the shaft (310), thereby keeping the first part (321) fixed relative to the shaft (310).

2. The limiting structure applied in a confined space according to claim 1, characterized in that, The limiting member (130) has an inner edge (131) that extends radially inward into the limiting groove (120), and the inner edge (131) abuts against the groove wall of the limiting groove (120).

3. The limiting structure applied in a confined space according to claim 1, characterized in that, The limiting member (130) has an outer edge (132) that protrudes radially outward from the limiting groove (120) and abuts against the end face of the first part (321).

4. The limiting structure applied in a confined space according to claim 1, characterized in that, The limiting member (130) is formed by a strip plate spirally wound around the central axis (310) in a corrugated manner to form a spiral coil with more than one turn. The spiral coil has some overlapping areas along the axial projection direction of the central axis, forming a peak (133) and a trough (134).

5. The limiting structure applied in a confined space according to claim 1, characterized in that, The limiting member (130) is open-ring shaped and has a first end (135), a second end (136), and a spiral body connecting the first end (135) and the second end (136) with at least one turn.

6. The limiting structure applied in a confined space according to claim 1, characterized in that, The limiting groove (120) has a first wall (122) disposed opposite to the opening (121) of the limiting groove (120), and the inner circumferential surface (137) of the limiting member (130) abuts against the first wall (122) to limit the radial displacement of the limiting member (130) relative to the shaft (310).

7. The limiting structure applied in a confined space according to claim 1, characterized in that, The limiting groove (120) has a second wall (123) connected to the groove (121) of the limiting groove (120) and disposed opposite to the first part (321). The elastic restoring force of the limiting member (130) abuts against the end face of the second wall (123) and the first part (321) in a pre-tightened state to limit the axial displacement of the first part (321) relative to the shaft (310).

8. The limiting structure applied in a confined space according to claim 1, characterized in that, The limiting groove (120) has a second wall (123) connected to the groove (121) of the limiting groove (120) and disposed opposite to the first part (321). The axial deformation of the limiting member (130) is greater than the distance between the end face of the second wall (123) and the first part (321).

9. The limiting structure applied in a confined space according to claim 1, characterized in that, The limiting member (130) has a first state in which no axial force is applied and a second state in which an axial force is applied. During the process of changing from the first state to the second state, the area covered by the radial projection of the limiting member (130) tends to increase or remain unchanged.

10. The limiting structure applied in a confined space according to claim 1, characterized in that, The limiting member (130) has at least one abutment point, which abuts against a local point on the end face of the first portion (321) in a point-contact manner; or, The limiting member (130) has at least one abutting surface, which abuts against a portion or all of the end face of the first portion (321) in a surface-contact manner; or, The limiting member (130) has at least one abutment point and at least one abutment surface. The abutment point abuts against a local point on the end face of the first part (321) in a point-contact manner, and the abutment surface abuts against a local area on the end face of the first part (321) in a surface-contact manner; or, The limiting member (130) has at least one abutment point, and each abutment point is integrally formed with the body of the limiting member (130); or, The limiting member (130) has at least one abutting surface, and each abutting surface is integrally formed with the body of the limiting member (130); or, The limiting member (130) has at least one abutment point and at least one abutment surface, and each abutment point and each abutment surface is integrally formed with the body of the limiting member (130); or, The limiting member (130) has at least one abutment point, and the projections of each abutment point along the axial direction are dispersed or uniformly distributed on the end face of the first part (321); or, The limiting member (130) has at least one abutting surface, and the projections of each abutting surface along the axial direction are dispersed or uniformly distributed on the end face of the first part (321); or, The limiting member (130) has at least one contact point and at least one contact surface, and the projections of each contact point and each contact surface along the axial direction are dispersed or uniformly distributed on the end face of the first part (321).

11. A robotic arm, characterized in that, include: The robotic arm body (200), at least one arm body and end effector assembly (400), at least one of the arm bodies is provided with a shaft (310), a rotary support element (320), a pulley (330), and a limiting structure (100) for use in a limited space as claimed in any one of claims 1-10, wherein the pulley (330) is sleeved and fixed to a second part (322) of the rotary support element (320), and the second part (322) is rotatable relative to the first part (321).

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