Variable amplitude vibration generator for compaction machine

A variable amplitude vibration generator for a compaction machine, comprising:

• a shaft rotatable about an axis of rotation extending longitudinally therethrough;
• a weight member defining an elongate mounting slot having a pair of opposed parallel planar sides between which a mounting area of said shaft extends, said mounting area including parallel planar surfaces disposed in sliding abutment with said planar sides whereby movement of said weight member relative to said shaft in a circumferential direction about the axis of rotation is prevented but movement of said weight member relative to said shaft in a radial direction orthogonal to the axis of rotation and coplanar with the circumferential direction is permitted;
• and
• a positioning arm disposed on said shaft and rotatable about the axis of rotation relative to both said shaft and said weight member, said weight member also defining an elongate positioning slot and said positioning arm including an axially extending portion defining a cam surface disposed through said positioning slot for slidable movement against said weight member along a length of said positioning slot, said positioning slot extending along said length from an end thereof away from said axis of rotation and then extending in closer proximity to said axis of rotation so that rotation of said positioning arm relative to both said shaft and said weight member moves said weight member relative to said shaft in a radial direction orthogonal to the axis of rotation thereby altering the moment of inertia of said weight member about the axis of rotation and resulting in a different amplitude of vibration during rotation of said weight member.