Patent ID: 8807012

Claim:
An engine comprising: a reciprocating-piston expander comprising: an expander cylinder having an inlet and an outlet; a piston head slidable in said expander cylinder and together enclosing an expansion chamber accessible by the inlet and the outlet; an intake header in fluidic communication with the inlet for channeling working fluid from a pressurized fluid source into the expansion chamber; an exhaust header in fluidic communication with the outlet for channeling working fluid exhausted out from the expansion chamber; an inlet valve for controlling the flow of working fluid from the intake header through the inlet to effect a power stroke of the expander, said inlet valve comprising an inlet valve head and a resiliently biasing member arranged together as a harmonic oscillator so that the inlet valve head is moveable against an equilibrium restoring force of the resiliently biasing member from an unbiased equilibrium position located in the intake header to a biased closed position occluding the inlet, and so that upon releasing from the closed position the inlet valve head undergoes a single oscillation past the equilibrium position to an oppositely biased maximum open position and returns to a biased return position between the closed and equilibrium positions to choke the flow of working fluid and produce a pressure drop across the inlet valve causing the inlet valve to close, said inlet valve head protruding in part into the expansion chamber when in the closed position so as to enable the piston to bump open the inlet valve from the closed position and initiate the single oscillation of the inlet valve head; an outlet valve for controlling the flow of working fluid exhausted out through the outlet to the exhaust header during a return stroke of the expander, said outlet valve comprising an outlet valve head, stopper, and a resiliently biasing member arranged so that the outlet valve head is moveable against an equilibrium restoring force of the resiliently biasing member from a maximum open position located in the expansion chamber and delimited by the stopper, to a biased closed position occluding the outlet; an outlet valve closing member carried by one of the outlet valve head and the piston head and positioned therebetween so that when the other non-carrying one of the outlet valve head and the piston head comes in contact with the outlet valve closing member the outlet valve is moved by the outlet valve closing member from the maximum open position to the closed position ahead of the bump opening of the inlet valve; and periodic return means operably connected to the piston head for effecting the return stroke of the expander after each power stroke.