Piston ring

A piston assembly for reciprocation inside a cylinder having a generally cylindrical cylinder wall comprising in combination:

• a first piston section substantially cylindrical in shape having a top and bottom planar surface with a thin walled, open ended cylindrical adaptor defining an internal chamber fixed to one planar surface of the first section, said wall of said adaptor constructed to deflect elastically under circumferential loads;
• a second piston section having means to secure it to the first section and having a first generally cylindrical portion having a diameter smaller than the thin walled adaptor of said first section and a second portion substantially cylindrical in shape and substantially identical in diameter with the first piston section and an annular projection on said first portion adapted to engage said thin walled adaptor within said chamber adjacent said one planar surface to axially align said first and second piston sections whereby said thin walled adaptor can deflect toward the smaller diameter portion of said first cylindrical portion;
• and
• a piston ring between said first and second piston sections, said ring sealingly engaging the outside surface of the thin walled adaptor of said first piston section and adapted to engage a cylinder wall in sealing engagement so that fluid leakage between said ring and a cylinder wall and said ring and said piston is prevented.