Patent ID: 8690548

Claim:
A heat engine comprising a body defining a heat engine chamber, a valve assembly including a valve assembly body, a bore through said valve assembly body, a piston slidably received within said heat engine chamber, said piston having a piston rod slidably received in said bore of said valve assembly, said valve assembly and said piston rod acting to divide said heat engine chamber into a first chamber and a second chamber, each said first and second chamber including a wall, said valve assembly including a one-way inlet valve and a one-way outlet valve each in fluid communication with said first chamber and a compressor working fluid network, said piston including a first piston head slidably received in said first chamber and a second piston head slidably received in said second chamber, such that said first piston divides said first chamber into a power side and a compressor side, and second piston divides said second chamber into a power side and a compressor side, said first and second piston heads connected by said piston rod, a first shifting port positioned in said wall of said first chamber and fluidly coupled to said power side of said first chamber, and a second shifting port positioned in said wall of said second chamber and fluidly coupled to said power side of said second chamber, such that said first and second shifting ports are selectively blocked and unblocked by said respective first and second piston heads, and a shifting valve fluidly coupled to each said shifting port, wherein said shifting valve is selectively moved between a first position and a second position by power working fluid vapor delivered from either of said first and second shifting ports based upon the position of said first and second piston heads relative to said shifting ports, such that when said shifting valve is in said first position, said piston is moved in a first direction causing compressor working fluid to be drawn into said power side of said first chamber, and when said shifting valve is in said second position, said piston is moved in a second direction opposite to said first direction, causing compressor working fluid to be compressed and forced out of said compressor side of said first chamber.