Abstract: An oscillatory drive unit for use in an oscillating system to be oscillated substantially at the resonance point of the oscillating system, wherein the oscillating system includes a mass to be oscillated and a countermass to which the mass is connected by resilient coupling members. The oscillatory drive unit includes a piston-cylinder-component that is operatively connected to the mass and the countermass. The piston-cylinder-component includes a cylinder chamber and a piston. The piston is arranged for reciprocal movement between a first end position and a second end position. Gas is introduced under pressure into the cylinder chamber within an energizing range of piston positions defined by a first energizing position and a second energizing position of the piston, and gas is vented from the chamber within a venting range of piston positions defined by a first venting position and a second venting position of the piston.