US Patent 7082909 Free-piston device with electric linear drive

To provide a universally usable free-piston device with electric linear drive, comprising at least one piston receptacle with at least one piston device arranged for linear displacement in the piston receptacle, the piston device comprising a traveller device, and a stator device being arranged on the piston receptacle, and the at least one piston device being drivable under the action of a medium which expands in an expansion space, it is proposed that the piston stroke be variably adjustable via the linear drive such that the dead centers of the displacement of the piston device are definable.