Patent ID: 6863507

Claim:
Free-piston engine having an engine piston and a hydraulic piston cooperating with the engine piston, to which hydraulic piston a pressure in a high-pressure accumulator means or in a low-pressure accumulator is capable of being applied with the aid of a switchover valve, wherein between said hydraulic piston and said switchover valve a transformer valve assembly including a control piston is arranged, wherein a connection to said high-pressure accumulator means is capable of being controlled open via a control land of said control piston, and that said control piston receives application of a pressure in a hydraulic cylinder and the force of a control spring in a closing direction, and an output pressure from the switchover valve or a pressure from said high-pressure accumulator means in an opening direction, wherein a stroke of said control piston in the opening direction is limited by a stop before termination of the stroke of said hydraulic piston.