CN218082788U

CN218082788U - Positioning mechanism, rotary joint and mechanical arm

Info

Publication number: CN218082788U
Application number: CN202222430786.3U
Authority: CN
Inventors: 葛壮; 刘欢; 朱龙泉; 叶廷
Original assignee: Wuhan United Imaging Zhirong Medical Technology Co Ltd
Current assignee: Wuhan United Imaging Zhirong Medical Technology Co Ltd
Priority date: 2022-09-14
Filing date: 2022-09-14
Publication date: 2022-12-20
Anticipated expiration: 2032-09-14

Abstract

The utility model relates to a positioning mechanism, a rotary joint and an mechanical arm, wherein the positioning mechanism is used for positioning a first member and a second member which are connected in a rotating way, the positioning mechanism comprises a fixed disc, a positioning disc and a locking component, and the fixed disc is used for being fixed with the first member; the positioning plate is arranged between the fixed plate and the first component, can rotate relative to the fixed plate, and is used for being fixed with the second component; the locking component is connected with the fixed disc and comprises a limiting part which can be elastically abutted against the bottom of the positioning sliding groove; when the fixed disc and the positioning disc rotate relatively, the limiting part can be separated from the locking groove section of one positioning sliding groove and move to the locking groove section along the guide sliding groove section of the other positioning sliding groove.

Description

Positioning mechanism, rotary joint and mechanical arm

Technical Field

The utility model relates to the technical field of medical equipment, especially relate to a positioning mechanism, rotary joint and arm.

Background

With the continuous development of artificial intelligence technology and robot technology, robots play a role in more and more fields, replace or assist human beings in more and more work so as to better complete work, and with the continuous aging of the world population, the medical industry also faces huge pressure, so that the pressure can be relieved to a great extent by the addition of medical robots. Therefore, medical instruments such as mechanical arms are widely applied to auxiliary medical treatment, the mechanical arms can overcome the problems and the defects of the traditional medical treatment, provide a remote operation platform for doctors, and have the advantages of being accurate in positioning, stable in operation, safe, smooth and the like.

The locking and positioning assembly of the mechanical arm in the prior art can only lock the mechanical arm, and the function of self-positioning cannot be realized after manual unlocking.

SUMMERY OF THE UTILITY MODEL

In view of this, it is necessary to provide a positioning mechanism, a rotary joint and a robot arm, aiming at the problem that the locking and positioning assembly in the robot arm in the prior art cannot realize self-positioning.

A positioning mechanism for positioning rotationally coupled first and second members, the positioning mechanism comprising:

a fixed disk for fixing with the first member;

the positioning disc is arranged between the fixed disc and the first component, can rotate relative to the fixed disc, and is used for being fixed with the second component;

the locking component is connected with the fixed disk and comprises a limiting part which can be elastically abutted against the bottom of the positioning sliding groove;

when the fixed disc and the positioning disc rotate relatively, the limiting part can be separated from the locking groove section of one positioning sliding groove and move to the locking groove section along the guide sliding groove section of the other positioning sliding groove.

In one embodiment, each positioning sliding groove extends along the circumferential direction of the positioning disc, and the groove depth of the guide sliding groove section becomes gradually shallower from one end facing the locking groove section to the other end away from the locking groove section.

In one embodiment, each positioning chute comprises two guide chute sections and one locking chute section, and the locking chute section is positioned between the two guide chute sections;

and/or the groove width of the guide chute section is gradually reduced from one end facing the locking groove section to one end far away from the locking groove section, two adjacent positioning chutes are communicated with each other to define a clamping point between the two adjacent positioning chutes, the limiting part moves from one guide chute section to pass through the clamping point, and the limiting part can automatically slide into the other locking groove section along the extending direction of the other guide chute section adjacent to the clamping point.

In one embodiment, the limiting part is a spherical surface, and the maximum size of the groove depth of the guide groove section is smaller than the radius of the limiting part; the maximum size of the groove width of the guide chute section is smaller than the diameter of the limiting part.

In one embodiment, the deepest ends of two adjacent guide chute sections are communicated, and the bottoms of two adjacent guide chute sections define the locking chute section.

In one embodiment, when the limiting part moves towards the locking groove section along the guide groove section, the component force of the elastic force applied to the limiting part along the direction parallel to the guide groove section is more than twice of the friction force of the guide groove section on the limiting part.

In one embodiment, the fixed plate is provided with an avoiding hole corresponding to the positioning sliding groove, and the locking assembly comprises:

the guide sleeve is connected with the fixed disc, and an inner hole of the guide sleeve is communicated with the avoidance hole;

the elastic piece is pressed in the guide sleeve;

the limiting ball is arranged in the guide sleeve in a rolling mode and abuts against the elastic piece, the elastic piece exerts pressure on the limiting ball all the time, so that the limiting ball is located in the positioning sliding groove all the time, and the portion, abutting against the positioning sliding groove, of the limiting ball is the limiting portion.

In one embodiment, the locking assembly further comprises, interconnected:

the first adjusting piece is arranged in the guide sleeve and comprises a guide part and an abutting part which are connected with each other, the guide part is arranged at one end of the elastic piece departing from the limiting ball in a penetrating manner, and the end face of one end of the elastic piece departing from the limiting ball abuts against the abutting part;

and the second adjusting piece is connected with one end, deviating from the guide part, of the abutting part, and the position of the second adjusting piece along the axial direction of the guide sleeve is adjustable.

In one embodiment, the locking assembly further comprises:

the end cover is detachably connected to one end, away from the limiting ball, of the guide sleeve; the second adjusting piece penetrates through the end cover and can move relative to the end cover.

In one embodiment, the number of the guide sleeves corresponds to the number of the positioning chutes.

In one embodiment, the number of the guide sleeves is two.

A rotary joint comprising a positioning mechanism as described above, the rotary joint further comprising:

the rotating disc is fixedly connected with the positioning disc, an avoiding channel used for avoiding a part of the first component is arranged on each of the rotating disc and the positioning disc, and the rotating disc is used for being fixed with the second component.

In one embodiment, the rotary joint further comprises:

the cable protection cover is fixedly connected to the fixed disc, a space for a cable to pass through is formed in the cable protection cover, and the cable protection cover is used for protecting the cable;

and/or, the rotary encoder subassembly includes rotary encoder, supporting seat, support column and deformation reed, rotary encoder with deformation reed rotatable coupling, the one end of supporting seat with the fixed disk is connected, the other end with rotary encoder is connected, the one end of support column with the deformation reed is connected, the other end with the rolling disc is connected.

In one embodiment, the rotary joint further comprises a stop assembly, the stop assembly comprising:

the first limiting block is fixedly connected to the fixed disc;

the second limiting block is fixedly connected to the fixed disc and is spaced from the first limiting block in the circumferential direction of the fixed disc;

the connecting disc is fixedly connected to the rotating disc, a guide groove is formed in the inner side wall of the connecting disc, and the extending direction of the guide groove is consistent with the motion track of the rotating disc;

the connecting piece is arranged in the guide groove in a sliding manner, and the extending direction of the connecting piece is consistent with that of the guide groove;

one end of the first sliding block is fixed on the connecting piece, and the other end of the first sliding block extends in the direction back to the guide groove;

one end of the second sliding block is fixed on the connecting piece, the other end of the second sliding block extends in the direction away from the guide groove, and the first sliding block and the second sliding block are spaced in the extending direction of the connecting piece;

when the rotating disc rotates relative to the fixed disc along a first direction until the first sliding block abuts against the first limiting block, the rotating disc does not rotate continuously;

or when the rotating disc rotates relative to the fixed disc along a second direction until the second sliding block abuts against the second limiting block, the rotating disc does not rotate continuously;

wherein the first direction and the second direction are opposite.

In one embodiment, the included angle of the motion track of the first sliding block is greater than 180 degrees;

and the included angle of the motion track of the second sliding block is also larger than 180 degrees.

The mechanical arm comprises the rotary joint, wherein the first component is a fixed arm, the second component is a rotating arm, the fixed arm is fixedly connected with a fixed disc, and the rotating arm is fixedly connected with the rotating disc.

The utility model has the advantages that:

the utility model provides a positioning mechanism, rotary joint and arm, wherein, positioning mechanism is used for injecing the relative position of two components that rotate the connection, through setting up fixed disk and positioning disk into relative pivoted form, first component and fixed disk fixed connection, second component and positioning disk fixed connection to make the second component can rotate first component relatively. And set up the positioning disk between fixed disk and first component for after fixed disk and first component fixed connection, fixed disk and first component are spacing to the positioning disk in the axial direction of fixed disk, make positioning disk and fixed disk can only relatively rotate, and can not axial displacement. Through set up a plurality of location spouts on the positioning disk, set up the locking subassembly on the fixed disk, through the spacing portion elasticity butt with the locking subassembly in the spout of location to the realization is to the location of fixed disk. When the fixed disc and the positioning disc rotate relatively, the limiting part slides into the locking groove section, because the groove depth of the locking groove section is the deepest, the limiting part is pressed against the locking groove section under the action of elastic force, at the moment, if no external force acts, the limiting part can not be separated from the locking groove section, and correspondingly, the fixed disc and the positioning disc are relatively fixed; under the action of external force, the limiting part of the locking assembly is separated from the locking groove section, and can automatically move to the locking groove section along the extending direction of the guide groove section after entering the guide groove section of the other positioning sliding groove. Through the structural form, the relative locking and the automatic positioning from one position to the other position during the rotation process of the positioning disc relative to the fixed disc are realized. In addition, the positioning mechanism provided by the technical scheme can realize the above functions through a pure mechanical structure, not only has a simple structure, but also saves the production cost.

Drawings

Fig. 1 is a schematic structural view of a mechanical arm in an expanded state according to an embodiment of the present invention;

fig. 2 is a schematic structural view of a rotating arm in a robot arm according to an embodiment of the present invention;

fig. 3 is a schematic structural view of the mechanical arm according to the embodiment of the present invention in a contracted state;

fig. 4 is a schematic structural diagram of a positioning mechanism in a rotary joint according to an embodiment of the present invention;

fig. 5 is a schematic cross-sectional structure view of a positioning mechanism in a rotary joint according to an embodiment of the present invention;

fig. 6 is a schematic plan view of a positioning plate in the positioning mechanism according to an embodiment of the present invention;

fig. 7 is a schematic cross-sectional view taken along line B-B in fig. 6.

Fig. 8 is a schematic perspective view of another positioning plate in the positioning mechanism according to an embodiment of the present invention;

fig. 9 is a schematic plan view of a positioning plate in the positioning mechanism according to an embodiment of the present invention;

fig. 10 isbase:Sub>A schematic sectional view taken alongbase:Sub>A-base:Sub>A in fig. 9.

Fig. 11 is a schematic structural view of a positioning mechanism in a rotary joint provided by an embodiment of the present invention when a positioning plate is not installed;

fig. 12 is a schematic structural view of a positioning mechanism in a rotary joint according to an embodiment of the present invention at another viewing angle when no positioning plate is installed;

fig. 13 is a schematic cross-sectional view of a positioning mechanism in a rotary joint according to an embodiment of the present invention, when no positioning plate is installed;

fig. 14 is a schematic perspective view of a rotary joint in a robot arm according to an embodiment of the present invention;

fig. 15 is a schematic perspective view of a rotary joint in a robot arm according to an embodiment of the present invention from another perspective view;

fig. 16 is a schematic cross-sectional view illustrating a rotary joint in a robot arm according to an embodiment of the present invention;

fig. 17 is a schematic structural diagram of a limiting assembly in a rotary joint in a robot arm according to an embodiment of the present invention;

fig. 18 is a schematic structural diagram of a limiting assembly in a rotary joint of a robot arm at another viewing angle according to an embodiment of the present invention;

fig. 19 is a schematic structural view of a rotary disk in a rotary joint in a robot arm according to an embodiment of the present invention.

A fixed arm 1; a rotating arm 2; a rotary joint mounting port 21; a rotary joint 3; a positioning mechanism 31; a fixed disk 311; a relief hole 3111; a positioning plate 312; a positioning chute 3121; a locking groove section 3121a; a chute section 3121b; a locking assembly 313; a guide bush 3131; an elastic member 3132; a stop ball 3133; a first adjustor 3134; a second adjustor 3135; an end cap 3136; a rotating disk 32; an avoidance channel 321; a cable protective cover 33; a rotary encoder assembly 34; a rotary encoder 341; a support base 342; a support post 343; a deformable spring 344; a limiting component 35; a first stopper 351; a second stopper 352; a connecting disc 353; a guide groove 3531; the first slider 354; a second slider 355; and a connector 356.

Detailed Description

In order to make the above objects, features and advantages of the present invention more comprehensible, embodiments of the present invention are described in detail below with reference to the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein, as those skilled in the art will be able to make similar modifications without departing from the spirit and scope of the present invention.

In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and for simplicity of description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.

In the present invention, unless otherwise explicitly specified or limited, the terms "mounted," "connected," "secured," and the like are to be construed broadly, e.g., as being fixedly connected, detachably connected, or integrated; can be mechanically or electrically connected; they may be directly connected or indirectly connected through intervening media, or they may be interconnected within two elements or in a relationship where two elements interact with each other unless otherwise specifically limited. The specific meaning of the above terms in the present invention can be understood according to specific situations by those skilled in the art.

In the present application, unless expressly stated or limited otherwise, the first feature may be directly on or directly under the second feature or indirectly via intermediate members. Also, a first feature "on," "over," and "above" a second feature may be directly or diagonally above the second feature, or may simply indicate that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature may be directly under or obliquely under the first feature, or may simply mean that the first feature is at a lesser elevation than the second feature.

It will be understood that when an element is referred to as being "secured to" or "disposed on" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and the like as used herein are for illustrative purposes only and do not denote a unique embodiment.

Referring to fig. 1 to 3, fig. 1 shows a schematic structural diagram of a mechanical arm in an expanded state according to an embodiment of the present invention, an embodiment of the present invention provides a mechanical arm, which includes a rotary joint 3 as follows, the mechanical arm further includes a fixed arm 1 and a rotating arm 2, and the fixed arm 1 and the rotating arm 2 are rotatably connected through the rotary joint 3. As shown in fig. 2, one end of the swing arm 2 is provided with a swivel joint attachment opening 21, the swivel joint 3 is attached to the swivel joint attachment opening 21, and the fixing arm is connected to the swivel joint 3. Normally, the fixed arm 1 is in a fixed state, and the rotating arm 2 can rotate relative to the fixed arm 1. The mechanical arm provided by the embodiment has two states of unfolding and accommodating, and when the mechanical arm is in the unfolding state, as shown in fig. 1, the rotating arm 2 and the fixed arm 1 are relatively fixed when rotating to form an included angle of 180 degrees with each other; when the mechanical arm is in the storage state, as shown in fig. 3, the rotating arm 2 and the fixed arm 1 are fixed relative to each other when they rotate to form an included angle of 0 °. Of course, in other embodiments, the included angle between the rotating arm 2 and the fixed arm 1 may be set according to actual conditions, for example, the rotating arm 2 and the fixed arm 1 may have a requirement of multiple angles, and the multiple angles may be positioned and locked by selecting different rotating joints 3. Specifically, the mechanical arm is positioned and locked at multiple angles by the following positioning mechanism 31.

As will be understood with reference to fig. 4 to 13, the embodiment of the present invention further provides a positioning mechanism 31 for positioning a first member and a second member which are connected in rotation, the positioning mechanism 31 includes a fixed disk 311, a positioning disk 312 and a locking component 313, wherein the fixed disk 311 is used for fixing with the first member; the positioning disc 312 is arranged between the fixed disc 311 and the first member, the positioning disc 312 can rotate relative to the fixed disc 311, the positioning disc 312 is used for being fixed with the second member, a first side surface of the positioning disc 312 facing the fixed disc 311 is provided with a plurality of positioning sliding grooves 3121, each positioning sliding groove 3121 comprises a locking groove section 3121a and a sliding guide groove section 3121b which are mutually continuous, and the depth of the locking groove section 3121a is greater than that of the sliding guide groove section 3121b; the locking assembly 313 is connected to the fixed plate 311, and the locking assembly 313 comprises a limiting part which can elastically abut against the groove bottom of the positioning sliding groove 3121; when the fixed disk 311 and the positioning disk 312 rotate relatively, the limiting portion may be separated from the locking groove section 3121a of one positioning sliding groove 3121 and move into the locking groove section 3121a along the sliding guide groove section 3121b of the other positioning sliding groove 3121.

The utility model provides a positioning mechanism 31 is used for injecing the relative position of two components of rotating the connection, through setting up fixed disk 311 and positioning disk 312 into relative pivoted form, first component and fixed disk 311 fixed connection, second component and positioning disk 312 fixed connection to make the second component can rotate first component relatively. And positioning disk 312 is disposed between fixed disk 311 and the first member, so that after fixed disk 311 is fixedly connected to the first member, fixed disk 311 and the first member limit positioning disk 312 in the axial direction of fixed disk 311, so that positioning disk 312 and fixed disk 311 can only rotate relatively but cannot move axially. The positioning of the fixed disk 311 is achieved by providing a plurality of positioning slide grooves 3121 on the positioning disk 312, providing a locking assembly 313 on the fixed disk 311, and elastically abutting a limiting portion of the locking assembly 313 in the positioning slide grooves 3121. Wherein, each positioning sliding groove 3121 is provided as a locking groove section 3121a and a sliding guide groove section 3121b which are continuous with each other, and the groove depth of the locking groove section 3121a is set to be greater than the groove depth of the sliding guide groove section 3121b, when the fixed disk 311 and the positioning disk 312 relatively rotate, the limit part slides into the locking groove section 3121a, since the groove depth of the locking groove section 3121a is deepest, the limit part is pressed in the locking groove section 3121a under the action of elastic force, at this time, if there is no external force, the limit part itself cannot be separated from the locking groove section 3121a, accordingly, the fixed disk 311 and the positioning disk 312 relatively remain stationary; under the action of external force, the limiting portion of the locking assembly 313 is separated from the locking groove segment 3121a, and after entering the sliding guide groove segment 3121b of another positioning sliding groove 3121, the limiting portion can automatically move into the locking groove segment 3121a along the extending direction of the sliding guide groove segment 3121 b. Through the above structure, relative locking and automatic positioning from one position to another position during rotation of positioning plate 312 relative to fixed plate 311 are achieved. Moreover, the positioning mechanism 31 provided by the technical scheme can realize the above functions through a pure mechanical structure, so that the structure is simple, and the production cost is saved.

It should be noted that the positioning mechanism 31 provided in this embodiment may be used in any two structures that rotate relatively and need positioning, for example, when the positioning mechanism 31 provided in this embodiment is used in a robot arm, the fixed disk 311 is used to be fixedly connected to the fixed arm 1, and the positioning disk 312 is fixed relatively to the rotating arm 2, and the locking and positioning of the rotating arm relative to the fixed arm 1 are realized by the positioning mechanism 31 as above, where the positioning is that the rotating arm goes from the storage state to the expansion state, or goes from the expansion state to the storage state, and after a certain force is applied to the rotating arm by the positioning mechanism 31 as above, the rotating arm can automatically go from one state to the next state.

The structure of the positioning sliding groove 3121 is not limited, and in one embodiment, each positioning sliding groove 3121 extends along the circumferential direction of the positioning plate 312, and the groove depth of the guide sliding groove 3121b becomes gradually shallower from the end facing the locking groove 3121a to the end away from the locking groove 3121a. Through the arrangement, when the limiting portion is subjected to an external force along the circumferential direction of the positioning disc 312, so that the limiting portion is separated from the locking groove segment 3121a of one positioning sliding groove 3121 and enters the sliding groove segment 3121b of the next positioning sliding groove 3121, even if the external force on the limiting portion is cancelled, since the sliding groove segment 3121b has a gradually downward slope to the positioning groove segment, and an elastic force always applies a downward force F to the groove bottom of the positioning sliding groove 3121 on the limiting portion, the force F on the sliding groove segment 3121b is decomposed into a pressure F1 perpendicular to the sliding groove segment 3121b and a thrust F2 parallel to the extending direction of the sliding groove segment 3121b, under the action of the thrust F2, the limiting portion moves along the positioning sliding groove segment 3121 until the limiting portion moves into the locking groove segment 3121a, and since the groove depth of the locking groove segment 3121a is deepest, if no external force acts, the limiting portion cannot be separated from the locking groove segment 3121a, and the limiting portion and the positioning groove segment are mutually locked. The number of the chute sections 3121b in each positioning chute 3121 is not limited, and may be one or two, that is, the positioning chute 3121 may have a structure in which, as shown in fig. 6 and 7, one chute 3121 has one chute section 3121b and one locking chute section 3121a, and of any two adjacent positioning chutes 3121, the locking chute section 3121a in one positioning chute 3121 is adjacent to the chute section 3121b in the other positioning chute 3121, that is, the limiting portion directly enters the chute section 3121b of the next positioning chute 3121 after being separated from the locking chute section 3121a of one positioning chute 3121 by an external force, and automatically slides into the locking chute section 3121a of the positioning chute 3121 by the rotation of the positioning plate 312 under the combination of the slope of the chute sections 3121b and the elastic force. The positioning sliding groove 3121 having such a structure is simple in structure and easy to process, but can only rotate the positioning plate 312 in one direction relative to the fixed plate 311.

It should be noted that the movement of the above-mentioned limiting portion is relative, and the locking groove 3121a of the rotating disc 32 is rotated to abut against the limiting portion by the rotation of the positioning disc 312 through the immobilization of the limiting portion, so as to realize the automatic positioning of the positioning mechanism 31; the positioning plate 312 may be fixed, the limiting portion moves, and the limiting portion moves into the locking groove 3121a along the extending direction of the sliding guide groove 3121b, so as to position the positioning mechanism 31. When the positioning mechanism 31 provided in the present embodiment is used in a robot arm, automatic positioning is achieved by rotation of the positioning plate 312. For ease of understanding, the movement of the stopper portion will be described below. The basic principle of locking and positioning by rotation of the positioning plate 312 is the same as that of the position-limiting part, except that the positioning plate 312 is moved instead of the locking part.

Of course, the number of the guiding chute sections 3121b in one positioning chute 3121 may be two, specifically, as shown in fig. 8 to 9, each positioning chute 3121 includes two guiding chute sections 3121b and one locking chute section 3121a, and the locking chute section 3121a is located between the two guiding chute sections 3121b; and/or the groove width of the sliding groove section 3121b gradually decreases from one end toward the locking groove section 3121a to one end away from the locking groove section 3121a, and the two adjacent positioning sliding grooves 3121 communicate with each other to define a clamping point between the two adjacent positioning sliding grooves 3121, and the limiting portion moves from one sliding groove section 3121b to the clamping point, and the limiting portion can automatically slide into the other locking groove section 3121a along the extending direction of the other sliding groove section 3121b adjacent to the clamping point. Two guiding groove sections 3121b are provided in one positioning groove 3121 and the locking groove section 3121a is provided between the two guiding groove sections 3121b, such that the groove depth of the guiding groove sections 3121b at both sides of the locking groove section 3121a away from one end of the locking groove section 3121a is gradually reduced, such that after the limiting portion is pushed out of the locking groove section 3121a by external force, the pushing force is further continuously applied to the limiting portion until the limiting portion moves from the guiding groove section 3121b of one positioning groove 3121 past the clamping point and enters the guiding groove section 3121b of the other positioning groove 3121, and after the force applied to the limiting portion is removed, the limiting portion automatically slides into the other locking groove section 3121a along the extending direction of the guiding groove section 3121b, thereby achieving the relative positioning between the second member fixed with the positioning disc 312 and the first member fixed on the fixing disc 311. With this structure, the second member can be made to rotate both clockwise and counterclockwise relative to the first member. It should be noted that, for the groove bottom of the locking groove segment 3121a, it is preferable that the ends of the two adjacent sliding guide groove segments 3121b with the deepest depth communicate with each other, and the bottom of the two adjacent sliding guide groove segments 3121b defines the locking groove segment 3121a. The groove bottom of the locking groove section 3121a is a spherical surface or a V-shaped surface, so that when the limiting part is located at the locking groove section 3121a, the limiting part cannot rock in the locking groove section 3121a, and the locking between the two components is more stable and reliable.

Furthermore, the limiting part is a spherical surface, and the maximum size of the groove depth of the guide sliding groove section 3121b is smaller than the radius of the limiting part; the maximum dimension of the groove width of the sliding guide groove section 3121b is smaller than the diameter of the limiting portion. The maximum size of the groove depth of the sliding groove guiding section 3121b is set to be smaller than the radius of the limiting portion, and it is possible to prevent the limiting portion from being caught by the groove wall of the sliding groove guiding section 3121b, thereby causing a phenomenon of damaging the entire positioning mechanism 31. And the maximum size of the groove section of the guiding groove section 3121b is set to be smaller than the diameter of the limiting part, so that the bottom of the limiting part is abutted against the bottom of the guiding groove section 3121b, the groove edge or two side walls of the limiting part and the guiding groove section 3121b are prevented from being abutted against each other, the stability of the limiting part in the movement of the guiding groove section 3121b can be improved, and the risk that the limiting part is clamped by the groove wall of the guiding groove section 3121b can be reduced.

It should be noted that the positioning plate 312 provided in this embodiment has a certain requirement on the curvature of the guiding chute section 3121b, that is, the curvature of the guiding chute section 3121b needs to be such that when the limiting portion enters the downward-moving guiding chute section 3121b and the force on the limiting portion is removed, the limiting portion should be able to slide into the locking chute section 3121a along the extending direction of the guiding chute section 3121 b. Therefore, when the limiting portion moves along the sliding guide groove segment 3121b to the locking groove segment 3121a, the component force of the elastic force applied to the limiting portion along the direction parallel to the sliding guide groove segment 3121b is more than twice of the friction force of the sliding guide groove segment 3121b to the limiting portion in the positioning chute 3121 in the positioning plate 312 provided by this embodiment. With such an arrangement, the limiting portion can automatically slide along the extending direction of the guiding groove section 3121b under the action of the elastic force through the structure of the guiding groove section 3121b, so as to realize the self-positioning function of the positioning mechanism 31.

The self-positioning function of the positioning mechanism 31 is realized by the cooperation of the locking assembly 313 and the positioning slideway. In one embodiment, as will be understood with reference to fig. 11 to 13, the fixed plate 311 is provided with an avoiding hole 3111 corresponding to the positioning sliding groove 3121, the locking assembly 313 includes a guide bush 3131, an elastic member 3132 and a stop ball 3133, the guide bush 3131 is detachably connected to the fixed plate 311, and an inner hole of the guide bush 3131 is communicated with the avoiding hole 3111; the elastic member 3132 is pressed into the guide bush 3131; the limiting ball 3133 is rollably disposed in the guide bush 3131 and abuts against the elastic element 3132, the elastic element 3132 always applies pressure to the limiting ball 3133, so that the limiting ball 3133 is always located in the positioning sliding groove 3121, and a portion of the limiting ball 3133 abutting against the positioning sliding groove 3121 is a limiting portion. By attaching the guide bush 3131 to the fixed plate 311 and communicating the inner hole of the guide bush 3131 with the escape hole 3111 of the positioning plate 312, the check ball 3133 is partially located in the guide passage formed by the guide bush 3131 and the escape hole 3111 of the positioning plate 312, and partially exposed from the escape hole 3111 and can abut against the positioning sliding groove 3121. The limiting ball 3133 always tends to move towards the positioning sliding groove 3121 under the action of the elastic force of the elastic element 3132, and the limiting ball 3133 always abuts against the bottom of the positioning sliding groove 3121. With the above structure, when positioning disk 312 is rotated relative to fixed disk 311 by an external force, or fixed disk 311 is rotated relative to positioning disk 312 by an external force, relative positioning and locking of positioning disk 312 and fixed disk 311 are achieved.

It should be noted that the guiding bush 3131 and the fixed disk 311 may be integrated, that is, a structure with a through hole is processed on the fixed disk 311 when the fixed disk 311 is processed; or may be a split type, specifically, the guiding bush 3131 may be fixed on the fixing plate 311 by welding or screw-fitting, and the avoiding hole 3111 on the fixing plate 311 is communicated with the inner hole of the guiding bush 3131. The elastic member 3132 may be a spring or another elastic member, and the limiting ball 3133 may be a steel ball.

Further, the locking assembly 313 further comprises a first adjusting part 3134 and a second adjusting part 3135 which are connected with each other, the first adjusting part 3134 is arranged in the guide bush 3131, the first adjusting part 3134 comprises a guide part and a supporting part which are connected with each other, the guide part is arranged at one end of the elastic part 3132 departing from the limiting ball 3133 in a penetrating manner, and one end face of the elastic part 3132 departing from the limiting ball 3133 is supported against the supporting part; a second adjusting member 3135 is connected to an end of the abutting portion facing away from the guide portion, and a position of the second adjusting member 3135 along an axial direction of the guide bush 3131 is adjustable. Wear to establish on the guide part with the one end that elastic component 3132 deviates from spacing ball 3133 for the guide part plays the guide effect to elastic component 3132's removal, and then makes the removal of spacing ball 3133 in uide bushing 3131 more reliable and more stable. By connecting the second adjusting member 3135 with the end of the abutting portion of the first adjusting member 3134 facing away from the guide portion, and the position of the second adjusting member 3135 in the axial direction of the guide bush 3131 being adjustable, the position of the first adjusting member 3134 in the axial direction of the guide bush 3131 is made adjustable, so that the amount of compression of the spring within the guide bush 3131 is adjustable. Thus, during assembly, the amount of compression of the elastic element 3132 can be adjusted according to actual conditions to adjust the pre-pressure of the spring and thus the magnitude of the positioning force.

Further, the locking assembly 313 further comprises an end cap 3136, wherein the end cap 3136 is detachably connected to an end of the guide bush 3131 facing away from the stop ball 3133; the second adjusting element 3135 is disposed on the end cap 3136 and can move relative to the end cap 3136. By providing a removable end cap 3136 on the guide 3131, on the one hand, the manufacturing is facilitated and, on the other hand, the assembly of the entire locking assembly 313 is facilitated.

It should be noted that, in the present embodiment, the first adjusting member 3134 is a cylindrical member having a step, the smaller cross-sectional diameter is the guiding portion, and the larger cross-sectional diameter is the abutting portion. The second adjusting part 3135 is an adjusting screw having a thread on the end cap 3136, the adjusting screw is in threaded connection with the end cap 3136, and the first adjusting part 3134 and the second adjusting part 3135 can also be in threaded connection. And a locknut is arranged at one end of the second adjusting part 3135 departing from the first adjusting part 3134, and after the positioning force is adjusted to a proper position, the locknut is screwed, so that the situation that the impact load generated by the limiting ball 3133 causes the looseness of the adjusting screw, and the influence on the magnitude of the positioning force and the positioning function can be avoided. In addition, a small tapered hole is formed at the bottom of the avoiding hole 3111 of the fixed plate 311, which is in contact with the positioning steel ball, so that the positioning steel ball is prevented from completely falling out of the hole, and the positioning function is prevented from being failed.

In the present embodiment, the number of the guide bush 3131 corresponds to the number of the positioning sliding grooves 3121. The number of the guide bush 3131 is two. That is, two locking members 313 are provided on one fixed plate 311, and two positioning members are symmetrically provided with respect to the center of the fixed plate 311. This arrangement can improve the reliability and stability of positioning and locking of the entire positioning mechanism 31. Of course, the locking member 313 may be provided in plurality according to actual circumstances.

It should be noted that in the present embodiment, two positioning sliding grooves 3121 are provided on the positioning plate 312, that is, the positioning angle of the positioning mechanism 31 is two angles of 0 ° and 180 °. In other embodiments, a plurality of positioning sliding grooves 3121 can be arranged according to actual needs, so that a multi-angle self-positioning function is realized.

As shown in fig. 14 to 19, the embodiment of the present invention further provides a rotary joint 3, including the above positioning mechanism 31, the rotary joint 3 further includes a rotating disc 32, the rotating disc 32 is fixedly connected to the positioning disc 312, an avoiding channel 321 for avoiding a part of the first member is disposed on both the rotating disc 32 and the positioning disc 312, and the rotating disc 32 is used for being fixed with the second member. The second member is fixedly connected to the rotatable disc 32 by fixedly connecting the rotatable disc 32 to the positioning disc 312 such that the second member is fixed relative to the positioning disc 312. The escape passage 321 for the first member is provided on both the rotary disk 32 and the positioning disk 312 to facilitate the fixed connection of the first member with the fixed disk 311. Thereby effecting relative rotation of the first member with respect to the second member. And the positioning mechanism 31 as above is provided in the rotary joint 3 so that the rotating arm 2 and the fixed arm 1 connected by the rotary joint 3 can realize self-positioning and locking functions. The functions can be realized through a pure mechanical structure, the structure is simple, and the production cost is saved.

In one embodiment, as shown in fig. 14-16, the rotary joint 3 further includes a cable guard 33, and/or a rotary encoder assembly 34. The cable protection cover 33 is fixedly connected to the fixed disc 311, a space for a cable to pass through is formed in the cable protection cover 33, and the cable protection cover 33 is used for protecting the cable; the rotary encoder assembly 34 includes a rotary encoder 341, a support base 342, a support column 343 and a deformation spring 344, the rotary encoder 341 and the deformation spring 344 are rotatably connected, one end of the support base 342 is connected with the fixed disc 311, the other end is connected with the rotary encoder 341, one end of the support column 343 is connected with the deformation spring 344, and the other end is connected with the rotating disc 32. The cable protective cover 33 can fix the cable, and damage to the cable caused by rotation of the mechanical arm is avoided. The rotary encoder 341 disposed in the rotary joint 3 can detect the relative rotation angle between the rotary disk 32 and the fixed disk 311, so as to more conveniently record and understand the implementation position and state of the rotary arm 2. Specifically, the rotary encoder 341 is a multi-turn absolute value encoder capable of reading the number of turns and the rotation angle, and of course, the rotary encoder 341 is not limited to an absolute value encoder, and may be an incremental encoder, a potentiometer, or the like having an angle measurement function. The deformation spring 344 of the rotary encoder 341 is a thin steel sheet, which has a certain adaptability, so that the rotary encoder 341 can maintain a relatively stable state during the movement process.

In one embodiment, as shown in fig. 17 and 18, the rotary joint 3 further includes a limiting component 35, the limiting component 35 includes a first limiting block 351, a second limiting block 352, a connecting disc 353, a first sliding block 354 and a second sliding block 355, wherein the first limiting block 351 is fixedly connected to the fixed disc 311; the second stopper 352 is fixedly connected to the fixed disk 311 and spaced apart from the first stopper 351 in the circumferential direction of the fixed disk 311; the connecting disc 353 is fixedly connected to the rotating disc 32, a guide groove 3531 is formed in the inner side wall of the connecting disc 353, and the extending direction of the guide groove 3531 is consistent with the motion track of the rotating disc 32; the connecting disc 353 is arranged in the guide groove 3531 in a sliding mode, and the extending direction of the connecting piece 356 is consistent with the extending direction of the guide groove 3531; one end of the first sliding block 354 is fixed to the connecting member 356, and the other end extends away from the guide groove 3531; one end of the second sliding block 355 is fixed to the connecting member 356, and the other end extends in a direction away from the guide groove 3531, and the first sliding block and the second sliding block are spaced in the extending direction of the connecting member 356; when the rotating disc 32 rotates relative to the fixed disc 311 along the first direction until the first sliding block 354 abuts against the first stop block 351, the rotating disc 32 does not rotate any more; or, when the rotating disc 32 rotates relative to the fixed disc 311 along the second direction until the second sliding block 355 abuts against the second stopper 352, the rotating disc 32 does not rotate any more; wherein the first direction and the second direction are opposite.

In this embodiment, the first direction may be a clockwise direction, and the second direction may be a counterclockwise direction. The first stopper 351 and the second stopper 352 are fixed to the fixed disk 311 at a distance from each other, and the first slider 354 and the second slider 355 are connected to each other by the connecting member 356, and then the connecting member 356 is slidably connected to the guide groove 3531 of the connecting disk 353 fixed to the rotary disk 32. When the rotating disc 32 rotates clockwise, the locking assembly 313 in the positioning mechanism 31 interacts with the locking groove 3121a to lock the rotating disc 32, if an external force acts on the arm of the rotating arm 2, after the locking of the positioning mechanism 31 is triggered and unlocked, the rotating arm 2 rotates under the action of the external force, and when the first sliding block 354 abuts against the first limiting block 351, the first limiting block 351 limits the first sliding block 354, and the rotating disc 32 cannot rotate continuously. On the contrary, when the rotating disc 32 rotates in the counterclockwise direction, the rotating arm 2 is also locked by the mutual cooperation of the locking component 313 and the locking groove 3121a, when the rotating arm 2 receives an external force, and after the locking is triggered, the rotating arm 2 continues to rotate in the counterclockwise direction until the second sliding block 355 abuts against the second limiting block 352, the second limiting block 352 limits the second sliding block 355, the rotating disc 32 cannot continue to rotate, and accordingly, the rotating arm 2 cannot continue to rotate. Through the arrangement, on one hand, the rotating arm 2 after being collided by mistake can be limited, so that the mechanical arm can be ensured to continue to work in a corresponding state; on the other hand, the cable in the mechanical arm is protected.

Further, the included angle of the motion track of the first sliding block 354 is greater than 180 degrees; the included angle of the motion path of the second slider 355 is also greater than 180 degrees. In this embodiment, the included angles between the movement tracks of the first sliding block 354 and the second sliding block 355 are set to be greater than 180 degrees, so that the entire robot arm is limited by the limiting component 35 after the locking state of the positioning mechanism 31 is triggered first, and the robot arm can also work normally without collision, thereby improving the reliability of use of the robot arm.

Specifically, as will be understood with reference to fig. 17 and 18, the first stopper 351, the second stopper 352, the first sliding block 354, and the second sliding block 355 are arranged in this order in the circumferential direction of the rotary joint 3, and the first stopper 351 and the first sliding block 354 have the same height in the axial direction, the second stopper 352 and the second sliding block 355 have the same height in the axial direction, the height of the bottom surface of the first stopper 351 is higher than the height of the top surface of the second sliding block 355, and the height of the bottom surface of the first sliding block 354 is higher than the height of the top surface of the second stopper 352; and the included angle between the first sliding block 354 and the second sliding block 355 is greater than the included angle between the first stopper 351 and the second stopper 352. Through setting up first sliding block 354 and second sliding block 355 one high one low, correspondingly, set up first stopper 351 and second stopper 352 one high one low, when rotor arm 2 rotates along clockwise, first sliding block 354 passes through second stopper 352 earlier, then continues to rotate to leaning on with first stopper 351 when, and connecting piece 356 slides to can not move the back again in guide way 3531, and first stopper 351 is spacing to first slider. This achieves that the trajectory of the first sliding block 354 has an angle greater than 180 degrees. Correspondingly, the second stopper 352 limits the second sliding block 355, and the second sliding block 355 firstly passes through the first stopper 351 and then abuts against the second stopper 352.

The utility model provides a locking and the location principle of arm as follows:

when the mechanical arm is adjusted from the retracted state to the deployed state, the rotating arm 2 needs to be manually pulled, so that the rotating arm 2 rotates relative to the fixed arm 1, and when the rotating arm 2 rotates until the limiting ball 3133 passes through the clamping point and enters the sliding guide groove section 3121b in the other positioning sliding groove 3121, the rotating arm 2 can automatically move into the locking groove section 3121a and is kept at the position under the action of the spring. If the rotating arm 2 is collided such that the locking of the restricting ball 3133 with the locking groove section 3121a is triggered, the continued rotation of the rotating arm 2 is restricted by the restricting assembly 35. Accordingly, the same principle applies from the deployed state to the stowed state. The mechanical arms above need to manually pull the rotating arm 2 to a position crossing the clamping point, and the rotating arm 2 can realize an automatic positioning function, that is, the limiting ball 3133 can automatically move to the locking groove section 3121a of the positioning sliding groove 3121 under the action of elastic force and keep a certain fixing force.

The utility model provides a arm with multi-angle is from positioning function is used for but not limited to medical robot and doctor's mutual location and uses the scene, also can be used in other equipment or the field that need mutual location.

All possible combinations of the technical features of the above embodiments may not be described for the sake of brevity, but should be considered as within the scope of the present disclosure as long as there is no contradiction between the combinations of the technical features.

The above-mentioned embodiments only represent some embodiments of the present invention, and the description thereof is specific and detailed, but not to be construed as limiting the scope of the present invention. It should be noted that, for those skilled in the art, without departing from the spirit of the present invention, several variations and modifications can be made, which are within the scope of the present invention. Therefore, the protection scope of the present invention should be subject to the appended claims.

Claims

1. A positioning mechanism for positioning a first member and a second member in rotational connection, the positioning mechanism comprising:

a fixed disk (311) for fixing with the first member;

the positioning disc (312) is arranged between the fixed disc (311) and the first component, the positioning disc (312) can rotate relative to the fixed disc (311), the positioning disc (312) is used for being fixed with the second component, a plurality of positioning sliding grooves (3121) are formed in the first side face, facing the fixed disc (311), of the positioning disc (312), each positioning sliding groove (3121) comprises a locking groove section (3121 a) and a sliding guide groove section (3121 b) which are continuous with each other, and the depth of the locking groove section is greater than that of the sliding guide groove section;

the locking component (313) is connected to the fixed disc (311), and the locking component (313) comprises a limiting part which can be elastically abutted against the bottom of the positioning sliding groove;

when the fixed disc and the positioning disc rotate relatively, the limiting part can be separated from a locking groove section (3121 a) of one positioning sliding groove (3121) and can move into the locking groove section (3121 a) along a sliding guide groove section (3121 b) of the other positioning sliding groove (3121).

2. The positioning mechanism according to claim 1, wherein each positioning sliding groove (3121) extends along a circumferential direction of the positioning plate (312), and a groove depth of the guide sliding groove section (3121 b) becomes gradually shallower from an end toward the locking groove section (3121 a) to an end away from the locking groove section (3121 a).

3. The positioning mechanism according to claim 2, wherein each positioning chute (3121) comprises two of the chute sections (3121 b) and one of the locking chute sections (3121 a), the locking chute section (3121 a) being located between the two chute sections (3121 b);

and/or the groove width of the sliding groove guiding section (3121 b) gradually decreases from one end facing the locking groove section (3121 a) to one end far away from the locking groove section (3121 a), and two adjacent positioning sliding grooves (3121) are communicated with each other to define a clamping point between the two adjacent positioning sliding grooves (3121), the limiting part moves from one sliding groove guiding section (3121 b) to the clamping point, and the limiting part can automatically slide into the other locking groove section (3121 a) along the extending direction of the other sliding groove guiding section (3121 b) adjacent to the clamping point.

4. The positioning mechanism according to claim 3, wherein the limiting portion is a spherical surface, and the maximum dimension of the groove depth of the guiding-sliding groove section (3121 b) is smaller than the radius of the limiting portion; the maximum size of the groove width of the sliding guide groove section (3121 b) is smaller than the diameter of the limiting part.

5. A positioning mechanism according to claim 3, wherein the ends of two adjacent guiding groove segments (3121 b) with the deepest depth communicate, and the bottoms of two adjacent guiding groove segments (3121 b) define the locking groove segment (3121 a).

6. The positioning mechanism according to claim 5, wherein when the stopper portion moves along the sliding guide groove section (3121 b) toward the locking groove section (3121 a), a component force of an elastic force applied to the stopper portion in a direction parallel to the sliding guide groove section (3121 b) is more than twice as large as a frictional force of the sliding guide groove section (3121 b) against the stopper portion.

7. The positioning mechanism according to any one of claims 1-6, wherein the fixed plate is provided with an avoiding hole (3111) corresponding to the positioning sliding groove (3121), and the locking assembly (313) comprises:

the guide sleeve (3131) is connected with the fixed disc (311), and an inner hole of the guide sleeve (3131) is communicated with the avoiding hole (3111);

an elastic member (3132) pressed into the guide bush (3131);

the limiting ball (3133) is arranged in the guide sleeve (3131) in a rolling manner and abuts against the elastic piece (3132), the elastic piece (3132) always exerts pressure on the limiting ball (3133) so that the limiting ball (3133) is always located in the positioning sliding groove (3121), and the portion, abutting against the positioning sliding groove (3121), of the limiting ball (3133) is the limiting portion.

8. The positioning mechanism according to claim 7, wherein said locking assembly (313) further comprises, interconnected:

the first adjusting piece (3134) is arranged in the guide sleeve (3131), the first adjusting piece (3134) comprises a guide portion and a supporting portion which are connected with each other, the guide portion penetrates through one end, deviating from the limiting ball (3133), of the elastic piece (3132), and one end face, deviating from the limiting ball (3133), of the elastic piece (3132) is supported against the supporting portion;

a second adjusting element (3135) connected to an end of the abutment portion facing away from the guide portion, a position of the second adjusting element (3135) along an axial direction of the guide bush (3131) being adjustable.

9. The positioning mechanism according to claim 8, wherein the locking assembly (313) further comprises:

an end cover (3136) detachably connected to one end of the guide bush (3131) facing away from the limiting ball (3133); the second adjusting piece (3135) is arranged on the end cover (3136) in a penetrating mode and can move relative to the end cover (3136).

10. Positioning mechanism according to claim 7, wherein the number of guide sleeves (3131) corresponds to the number of positioning runners (3121).

11. The positioning mechanism according to claim 10, wherein the number of guide sleeves (3131) is two.

12. A rotary joint comprising a positioning mechanism according to any one of claims 1 to 11,

the rotary joint (3) further comprises:

the rotating disc (32) is fixedly connected to the positioning disc (312), an avoiding channel (321) used for avoiding a part of the first component is arranged on each of the rotating disc (32) and the positioning disc (312), and the rotating disc (32) is used for being fixed with the second component.

13. The rotary joint according to claim 12, characterized in that the rotary joint (3) further comprises:

the cable protection cover (33) is fixedly connected to the fixed disc (311), a space for the cable to pass through is formed in the cable protection cover (33), and the cable protection cover (33) is used for protecting the cable;

and/or, rotary encoder subassembly (34) includes rotary encoder (341), supporting seat (342), support column (343) and deformation reed (344), rotary encoder (341) with deformation reed (344) rotatable coupling, the one end of supporting seat (342) with fixed disk (311) is connected, the other end with rotary encoder (341) is connected, the one end of support column (343) with be connected deformation reed (344), the other end with the rolling disc (32) is connected.

14. The rotary joint according to claim 12, characterized in that the rotary joint (3) further comprises a stop assembly (35), the stop assembly (35) comprising:

a first stopper (351) fixedly connected to the fixed disk (311);

a second stopper 352 fixedly connected to the fixed disk 311 and spaced apart from the first stopper 351 in a circumferential direction of the fixed disk 311;

the connecting disc (353) is fixedly connected to the rotating disc (32), a guide groove (3531) is formed in the inner side wall of the connecting disc (353), and the extending direction of the guide groove (3531) is consistent with the movement track of the rotating disc (32);

the connecting piece (356) is arranged in the guide groove (3531) in a sliding mode, and the extending direction of the connecting piece is consistent with the extending direction of the guide groove (3531);

a first sliding block (354) having one end fixed to the connecting member (356) and the other end extending in a direction away from the guide groove (3531);

a second sliding block (355) having one end fixed to the connecting member (356) and the other end extending in a direction away from the guide groove (3531), the first sliding block (354) and the second sliding block (355) being spaced apart in the extending direction of the connecting member (356);

when the rotating disc (32) rotates relative to the fixed disc (311) along a first direction until the first sliding block (354) abuts against the first limiting block (351), the rotating disc (32) does not rotate continuously;

or when the rotating disc (32) rotates relative to the fixed disc (311) along a second direction until the second sliding block (355) abuts against the second limiting block (352), the rotating disc (32) does not rotate any more;

wherein the first direction and the second direction are opposite.

15. The rotary joint according to claim 14, wherein the included angle of the motion trajectory of the first sliding block (354) is greater than 180 degrees;

the included angle of the motion track of the second sliding block (355) is larger than 180 degrees.

16. A robot arm, characterized in that it comprises a revolute joint (3) according to any one of claims 12-15, wherein said first member is a fixed arm (1) and said second member is a revolute arm (2), said fixed arm (1) being fixedly connected to said fixed disc (311) and said revolute arm (2) being fixedly connected to said revolute disc (32).