Abstract: A seal comprises a support member having an outer periphery of substantially circular form, and a resilient seal member mounted upon the support member, the seal member, when occupying a relaxed condition, having an outer periphery of generally circular form and a diameter greater than that of the support member, the seal member and support member being eccentric to one another when the seal member occupies the relaxed condition, the seal member being compressible towards a compressed condition in which the seal member and the support member are of substantially equal diameter and are substantially coaxial.

Abstract: This invention relates to piston compression ring assemblies, each of which consists of a main ring element and an auxiliary ring element. The assemblies can by themselves adjust the radial gaps between the assemblies and the liner, and the gaps between the assemblies and the liner, and the gaps between the assemblies and the wall of the ring groove in the piston. The two ring elements engage with each other on their flat sides, and there is a notch for accommodating lubrication oil provided in the engaging portion. The radial cuts in each ring element stagger each other by an angle of 180.degree.. The two ring elements are good sealing and lubricating, respectively, therefore they can reduce the leakage of gas and the compensation of oil, and have a long period of use. They can thus improve the efficiency and the power of internal combustion engine, and reduce the emission and the noise of the internal combustion engine.

Abstract: A piston ring having a keystone shape and an orientation feature on one of its surfaces for ensuring proper orientation of the ring during installation. The piston ring preferably has an outer peripheral surface that includes a sealing land with a nitride hardened surface to resist wear during the service life of the piston ring. A tapered surface is also provided on the outer peripheral surface adjacent to the sealing land.