PURPOSE: To simply obtain the variation of angular speed by mechanical control by forming a pulley installed on a driving shaft into a regular-polygonal or an elliptical shape and shifting the position of a driven side pulley with respect to the driving shaft side pulley.
CONSTITUTION: A regular-polygonal or elliptical shaped gear pulley 2 is installed on a driving shaft 1. A pulley 6 installed on a driven shaft 8 is formed with a regular-polygonal or elliptical shaped one at a multiple of integer or a fraction of integer of the driving shaft side pulley 2. The position of the driven side pulley 6 is shifted by π/m (m = the number of angles) with respect to the driving shaft side pulley 2. Thus, the variation of angular speed can be simply obtained by means of mechanical control.