Piston rings with control slits

A piston ring suitable for use on a movable member, such as a piston, operating on a cylindrical surface, such as a cylinder liner, said piston ring having a first support surface resting on a first side of a groove circumferentially provided in the movable member and a second support surface resting on a second and opposite side of said groove, said first and second sides being transversally disposed relative to said movable member, said piston ring comprising a plurality of control means on said support surfaces and axially disposed relative to the thickness of said piston ring for simultaneously controlling elastic and thermal deformations of said ring and heat flowing across said ring in various positions of said ring assumed during motion thereof.