A piston and ring assembly.

摘要

A piston and ring assembly is operative in a cylindrical bore wall to retain fluid to one side of the assembly. A piston has at least one annular stepped groove in the side wall of the piston, with the groove being stepped into uppermost and lowermost spaces with the uppermost space having the greatest depth. At least two split compression rings are in the groove, effective to each substantially annularly engage the bore wall, the rings having mating surfaces superimposed one upon another and having their split ends out of superimposed alignment. A solid lubricant coats essentially all of the groove and constitutes the non-mating surfaces of the superimposed rings. Pressure of the retained fluid forces the rings together to act in unison and seal jointly against both the step and a side of the groove opposite the retained fluid.