Blue disk has sliding joint (3 cylindrical pins) with glass pulley and both can rotate around pink fixed worm. Glass pulley can move axially but the disk not.
Yellow worm wheel and orange cam (an eccentric) are fixed together and rotate on a pin of the blue disk thanks to the fixed worm. Violet roller mounted on the pulley is forced toward the cam by three green springs.
A moving strip (not shown) makes the glass pulley and the blue disk rotate by friction. At the same time the pulley slowly reciprocates axially under action of the cam and roller, thus gives the strip lateral motion.
Red screw is for reducing axial stroke of the pulley (limiting its motion to the right).