Patent ID: 7076941

Claim:
An externally heated engine comprising: a) a first piston adapted for movement within a first cylinder said first piston having a first side and a second side opposite the first side, the first side of the first piston and the first cylinder defining a first working chamber and the second side of the first piston and the first cylinder defining a first opposite chamber containing a controlled pressure opposing fluid; b) a second piston adapted for movement within a second cylinder, said second piston having a first side and a second side opposite the first side, the first side of the second piston and the second cylinder defining a second working chamber and the second side of the second piston and the second cylinder defining a second opposite chamber the second opposite chamber containing a controlled pressure opposing fluid; c) a closed fluid path between the first and second cylinders, the closed fluid path including a controlled pressure working fluid, the working fluid capable of moving between the first working chamber and the second working chamber, a pressure differential between the first working fluid and the opposing fluid in the first opposite chamber between 4 PSI and 500 PSI; d) a regenerator within the closed fluid path; e) a heater for heating the working fluid in the first cylinder; f) a heat extractor for cooling the working fluid in the second cylinder to a temperature of below 32° Fahrenheit; and g) the first piston and the second piston arranged to reciprocate such that the volume of the working fluid is compressed and expanded alternately such that the ratio of the expanded volume to the compressed volume is greater than 2 to 1.