Über verzweigungslagen bei sphärischen viergelenkgetrieben

In discussing the laws of motion of a specific linkage with variable parameters, the limiting or exceptional cases where a change-point position becomes possible is frequently of interest. In this paper it is explained how to obtain the ratios of velocities for spherical four-bar linkages with change-point positions. The positions of the relative pole axes 31 and 20 (i.e. motion of the input link with respect to the output link or motion of the coupler with respect to the fixed link) are of special interest. Passing to the limit leads to the corresponding plane four-bar linkages. Two examples, one linkage from the plane and one from spherical kinematics, conclude the paper.