Piston head assembly having an l-shaped piston ring

Claim 1

In a piston head assembly for reciprocation within a combustion cylinder and wherein said piston head is provided with an annular peripheral groove of L-shaped cross section at the top of said head and defining an upper peripheral portion offset radially inward from the balance of the piston periphery and wherein a sealing wear ring of generally L-shaped cross section formed of a generally horizontal portion and a generally vertical portion is correspondingly carried within said groove with the upper end of said vertical portion terminating below the top of said piston head and with a vertical wear surface common to both portions adapted to slide against the cylinder wall; the improvement wherein: said horizontal portion includes an upper radially extending surface inclined from the horizontal and facing a correspondingly inclined groove surface and the rear face of said vertical portion tapers outward and upward to define with said offset peripheral portion of said piston head a triangular shaped thrust area in cross sEction for opening directly to the combustion area at the top of the vertical portion of said ring for insuring gas force application tending to seal said ring to said cylinder and said piston groove carrying said ring, while facilitating gas flow to the gap maintained between the inclined upper surface of said horizontal portion and said opposing groove surface by said applied gas force.