Patent ID: 7895978

Claim:
A two-stroke internal combustion engine comprising: at least one cylinder having a bore diameter, a central axis, a cylinder wall, and an upper and a lower extremity; a piston slip-fit in the cylinder, the piston having an overall height and a top surface, an upper portion and a lower portion each of approximately the bore diameter, each of the upper and lower portions having at least one seal ring between the piston and the cylinder wall, and a central portion of significantly less than the bore diameter and a height at least one-half of the overall piston height, providing an unobstructed annular volume between the central piston portion and the cylinder wall; a crank mechanism coupled to the piston in a manner providing a repeating stroke of a specific stroke length in the direction of the central axis of the cylinder, the repeating stroke providing a varying volume V between the top of the cylinder and the top surface of the piston; one or more exhaust ports through the cylinder wall, each exhaust port having a first height in the direction of the cylinder axis, centered at a first dimension from the top of the cylinder; one or more intake ports through the cylinder wall, each intake port having a second height in the direction of the cylinder axis, centered at a second dimension from the top of the cylinder; and a forced-air mechanism providing air to the one or more intake ports; wherein for a significant portion of every stroke both the one or more exhaust ports and the one or more intake ports are open to the unobstructed annular volume between the central piston portion and the cylinder wall, allowing the forced-air mechanism to force air freely and without obstruction from the one or more intake ports around the central piston portion to the one or more exhaust ports.