Patent ID: 7654240

Claim:
A piston for an internal combustion engine, comprising; an upper crown having a top surface, a bottom surface opposite the top surface, and a side wall, the top surface being exposed to a combustion chamber of the engine; a lower crown having a side wall containing one or more annular ring grooves, an upper surface, and a lower surface opposite the upper surface, the upper crown is rigidly attached to the lower crown such that at least a part of the bottom surface of the upper crown contacts the upper surface of the lower crown; and a central air gap between the bottom surface and the upper surface, and a separate annular air gap positioned radially outwards of the central air gap and radially between the side wall containing ring grooves and the upper crown side wall, both the central air gap and the annular air gap having a predetermined pattern, and being sealed to prevent airflow into or out of the air gaps.