VDI VDI 2156 PDF

Spatial crank mechanisms are crank linkages possessing at least two axes of rotation which cross but do not intersect - in other words, skewed axes. When on the other hand all axes are axes of rotation and intersect at a single point, the mechanism in question is a spherical crank mechanism (see VDI 2154); if they are all parallel to each other, a planar crank mechanism (see VDI 2145) is defined. The standard is only concern with spatial crank mechanisms with the degree of freedom F = +1 which can be developed from spatial kinematic chains in which the number of links is the same as the number of joints. The technical background to this is dealt with in standard VDI 2127.

On the basis of a closed kinematic chain with a spatial arrangement of the joints, mechanisms are derived by defining one link as the frame. Chains which contain only binary links and are subject matter in this standard can have from three to seven links. The type, number and arrangement of the joints allow a wide range of designs (see Section 4).