Worm 1 rotates about axis A and can slide along this axis on shaft 3 along a feather key. Worm 1 drives worm wheel 2 about fixed axis B. Worm 1 is reciprocated by lever 4 which oscillates about fixed axis D and carries roller 6. Lever 4 is connected by an intermediate link to slide 5 which reciprocates along fixed guide a, whose axis is parallel to axis A, and is connected by a turning pair to worm 1. Roller 6 of lever 4 rolls and slides a long groove d of cylinder cam 7 which is rotated by a separate driye. If the profile of groove d is properly designed and the speed of cam 7 suitably selected, the angular velocity of wheel 2 can be varied periodically within definite limits.
$3176$CmL.ML$