The invention relates to an adjustment mechanism that includes a set ring gears which are arranged coaxially towards a central axis and which each include a cylindrical toothing system, two eccentric wheels with beveloid gears which mesh with the cylindrical toothing systems of the ring gears, eccentric axes which are inclined at an angle towards the central axis, and a central shaft that is driven by a drive shaft onto which the eccentric wheels are mounted. The set of ring gears include a center ring gear that is circulating and two outer neighboring ring gears which are solidly fixed.