Patent ID: 6941904
Filing Date: 2005-09-13
Classification: F02B

Abstract:
1. A free piston engine comprising: an energy storage and control assembly having a first side; a first combustion cylinder assembly located adjacent to the first side of the energy storage and control assembly and including a first cylinder liner that defines a generally circular first engine cylinder, which is centered about an axis of motion, with the first engine cylinder having a cylinder diameter; an inner piston assembly having a first inner piston located and telescopically slidable within the first engine cylinder along the axis of motion and an inner rod mounted to the first inner piston and operatively engaging the energy storage and control assembly; an outer piston assembly having a first outer piston located and telescopically slidable within the first engine cylinder along the axis of motion and having a first outer piston head facing the first inner piston and spaced farther from the energy storage and control assembly than the first inner piston, with the first outer piston including a first piston bridge located on an opposed end of the first outer piston from the first outer piston head, with the first piston bridge having an oval outer surface with a maximum diameter that is larger than the cylinder diameter of the first engine cylinder, and with the outer piston assembly including a first outer rod mounted to the first piston bridge and operatively engaging the energy storage and control assembly; and a first scavenge pump engaged with the first combustion cylinder and having a first scavenge pump housing, which defines an air inlet, an air outlet and includes a wall that defines a main pumping chamber selectively connectable to the air inlet and the air outlet, with the main pumping chamber telescopically receiving the first piston bridge therein and the wall being cylindrical in shape and having an oval cross section such that the oval outer surface of the first piston bridge seals against the wall.