Abstract: A synchronization device for an articulated parallelogram boom assembly having a floating frame connected between an upper work platform carrying boom assembly, and a lower vehicle mounted boom assembly. The synchronization device is mounted on the floating frame and includes a slidable member and compression and tension links connected between the slidable member and the upper and lower boom assemblies. The synchronization device is constructed and arranged to maintain the included angles of the adjacent upper and lower boom assemblies substantially identical during the luffing movement of the boom assemblies so that the work platform is maintained parallel to the ground plane.

Abstract: According to the depicted embodiment, two eccentric-weight units are rotated into or out of radial alignment with each other to cause an increase or diminution of vibration. The units are journaled in a frame and a coupling assembly causes both to rotate in unison, but the assembly is also operative to rotationally index one of the weight units relative to the other to vary the noted radial-alignment relationship, as desired. One of the weight units comprises a pair of separate weights, each having an eccentric-throw portion, which are separated along the rotation axis and which are joined for common rotation by a resilient coupling. The latter coupling sustains and reactively absorbs any misalignments and/or displacements arising between the separate weights. The other weight unit is an elongate, eccentric shaft coaxial with the separate weights.