Joints with multiple degrees of freedom, which are essential to three-dimensional parallel-motion mechanisms, have conventionally combined simple rotational joints. However, the complex structure of such joints can result in relatively large joints. Sliding spherical joints with multiple degrees of freedom have also been available, although these are often characterised by large frictional resistance and inner clearances.
In order to resolve these problems, Spherical Rolling Joints have been developed. These units utilise three-degree-of-freedom rolling guideways to provide high precision and rigidity with zero clearance. They are available worldwide from Heason Technology, the exclusive UK distributor and global sales office.
The spherical rolling joint (SRJ) is available in eight sizes and two precision grades. Standard precision grade has a runout less than +/-2mm; super precision class has a runout less than +/-1mm. The smallest SRJ has a 6.35mm diameter sphere in a housing of just 19mm diameter with a load capacity of 128N; the largest SRJ has a 76.2mm diameter sphere in a 136mm diameter housing with a load capacity of 16kN. Maximum swing angles are up to 40 degrees.
In each case the movable part has less frictional resistance due to its rolling joint structure under preload, thereby enabling the joint to achieve high precision with zero clearance.
Compared with joints combining rolling bearings with three degrees of freedom, the SRJ design offers higher rigidity in a smaller envelope.