DE102005029064A1 - Pivot system for parallel rods comprises ball attached to one rod which swivels inside coaxial hollow spherical shell, to which another rod is attached, this shell swiveling inside second shell, to which third rod is attached - Google Patents

Abstract

The pivot system for parallel rods, for use in robots and medical apparatus, comprises a ball attached to one rod (1). This swivels on the inner surface of a coaxial hollow spherical shell (3), to which another rod (2) is attached. The shell swivels inside a second coaxial shell (5), to which a third rod (4) is attached. This shell swivels in an outer socket (6).

Description

classification

mechanisms with parallel kinematic structure are increasingly used in the Machine tool construction, in robotics and handling technology and in motion tasks in medical technology. Most of the time is the frame connected to the output platform in such mechanisms with struts, the connection is often done with ball or universal joints. The calculation of many such mechanisms revealed that particular good transmission and motion characteristics can be achieved if multiple struts connected at one point to the frame or to the platform are.

With The invention presented here makes it possible to have several struts over one Ball joint connection can be connected. There remains every possible rotational movement each strut opposite every other strut received. The axes of rotation of all these rotations intersect at one point.

In the patent GB 2289002 Ball joints are presented in which 2 struts can be connected to the frame in one point. Two ball halves are connected via a rotary joint, so that one half of the ball can be rotated as desired with respect to the other. At each hemisphere one strut is firmly connected.

In patent GB 2289001 It is described how the ball formed by the two halves of the ball can be mounted in a further spherical shell, so that two further common rotational movements are possible. In the patent, the implementation of the storage of the spherical shells is described with a magnetic bearing.

In the company publication GAP HEX3 GB97 of the company Geodetic Technology (USA), Inc. Gaskins Center, 3827 Gaskins Road, Glen Allen, Virginia 23060 USA, will be for the movements described in the two patents mentioned above different types of bearings used (bearings and plain bearings).

In the patents GB 2288998 . GB 2269552 . GB 2329138 and US 5857815 describes cases of use for mechanisms of parallel structure in which the points of articulation of two struts coincide in one point.

Deficiencies of previous solutions

at the previous known solutions can not more than 2 struts connected to the frame (platform) in one point become.

Farther it is impossible the struts without another ball joint about its own axis twist.

Solved problem

parallel kinematic Structures can only light and stiff and with high dynamics and accuracy be built if they have a framework similar structure, because it only possible is only to have tensile and compressive loads in the structure. to Training of "truss nodes" it is necessary that the lines of action of several struts intersect at one point. For spatial Structures must 3 struts connected to the rack (platform) at a point to a force of any direction in only tensile and compressive forces at variable Safely disassemble struts directions.

explanation the invention and an embodiment

The ball joint allows two, three or more struts to be connected at one point, such that each strut is rotatable about all three axes of rotation with respect to each other strut. Kinematically equivalent is this connection, as if each strut with each other and each strut are connected to the frame via a ball joint and the axis of rotation of all possible rotations intersect at one point. The mutual movement of the individual joint elements is guided by the surface of concentric balls. The strut ( 1 ) is fixedly connected to a ball, wherein the strut axis intersects the ball center. At the strut ( 2 ) is half of a hollow ball attached which is provided with a recess. Through this recess, the strut ( 1 ). From the size of the recess depends on the pivoting angle, which between strut ( 1 ) and strut ( 2 ) becomes possible. Another half hollow sphere ( 3 ) adds the first half hollow sphere to a hollow sphere. Also, the center of the inner and outer spherical surface, the hollow sphere ( 2 . 3 ) and the strut axis of the strut ( 2 ) intersect at one point. The inner surface of the hollow sphere with the strut ( 2 ) and the surface of the ball with the strut ( 1 ) are sliding together. There are also bearings between two spherical surfaces imagine bar (eg rolling bearings). The difference in diameter of the two spherical surfaces determines the accuracy and the play of the joints.

With these two struts more can be connected in the same way, in which case the previous strut ( 2 . 3 ) the function of the strut ( 1 ) and the new strut ( 4 . 5 ) the function of the strut ( 2 . 3 ) takes over. By analogy, further strivings are attachable. Figure 1 shows the connection of 3 struts and a rack (platform) connection ( 6 . 7 ). In the embodiment according to Figure 1 is a rotation of the strut ( 1 ) possible at any angle. To all other axes of rotation are pivoting movements by 60 ° to max. 70 ° meaningful constructive feasible.

The Center position of these ± 30 ° - ± 35 ° pivoting movements is structurally displaceable around the arbitrarily selectable angle α, see picture 3.

at an execution according to picture 2 increases a tilt angle of each strut from approx. ± 30 ° - ± 35 ° up to ± 180 °.

The Construction on picture 2 is not in comparison to picture 1 so stiff executable. It is possible during assembly but not required in each case associated hollow ball halves with each other to connect (screw, pin connection or similar). constructive simple is the implementation of the ball joint connection via sliding compounds, depending on the application and load different sliding bearing materials and lubrication types come into question.

Advantages and user benefits

With Help of the ball joint connection it becomes possible a multiplicity of spatial to construct parallel kinematic mechanisms in such a way that only and pressure loads occur. Furthermore, it will be possible the singularity free To increase the working space of these mechanisms.

Claims (4)

Ball joint especially for parallel kinematic machine tools, for mechanisms in handling and robotics and mechanisms in medical engineering. characterized in that the intersections of the axes of a plurality of ball joints coincide in one point, and the mutual movement of the individual hinge elements is guided by the surfaces of concentric balls. Ball joint connection according to claim 1 in that the possible swivel range around a zero position takes place, which is an arbitrary orientation in the Has room. Ball joint connection according to claim 1 and 2 characterized in that the mutual movement of the individual Articulated elements through any guides (eg sliding guide, Rolling guide) can. Ball joint connection according to claim 1, 2 and 3 characterized in that the intersections of the axes due tolerances do not lie exactly on top of each other.