Abstract: A rotary piston machine has a housing in which are arranged at least two pistons which are able to revolve together in the housing about an axis of rotation which is fixed with respect to the housing, the pistons being mounted slidingly in a piston cage which is mounted in the housing and revolves together with the pistons about the axis of rotation, the two pistons executing mutually opposing reciprocating motions while revolving about the axis of rotation in order alternately to increase and decrease the volume of a working chamber defined by end faces oriented towards one another of the two pistons and by the piston cage, the axis of rotation passing through the working chamber and the piston cage having a gas exchange opening for admitting and discharging gas to and from the working chamber.

Abstract: An ultra light poppet valve for an internal combustion engine. The valve is formed by cold forming a blank into an elongated cup having an extremely thin wall and a flared open end onto which a cap is welded, the bottom end of the cup which defines the tip end of the valve having a wall section which is substantially of the thickness of the original blank. In accordance with one aspect of the invention, a keeper groove is formed adjacent the tip end as part of the cold forming process.