Arm 1 is keyed to shaft 7 and rotates clockwise about fixed axis A. Pivoted to the ends of arm 1 are concentrically mounted roller 2 and eccentrically mounted roller 3. By means of ratchet device 4, bushing a, on which roller 3 is eccentrically mounted, is periodically turned through a definite angle, so that roller 3 is moved either toward or away from axis A. When roller 2 engages the suitably profiled cam surfaces of levers (followers) 5 and 6, which oscillate about fixed axis B, the levers have a constant amplitude. The amplitudes of levers 5 and 6 gradually vary when they are engaged by roller 3.
$3174$CmL,ML$