Engines and compressors

A machine comprising a frame, a crankshaft rotatably mounted in the frame, a plurality of pairs of cylinders integral with the frame, the cylinders in each pair being disposed on opposite sides of the axis of the crankshaft and each pair of cylinders being angularly and axially separated around the crankshaft axis, means for allowing fluid to pass into each cylinder at one pressure and for allowing fluid to pass out of each cylinder at another pressure, the crankshaft having one crankpin for each plurality of pairs of cylinders, each crankpin having an axis which is eccentric relative to the crankshaft axis, a plurality of discs equal in number to the number of pairs of cylinders and each disc being rotatably mounted on each crankpin between the cylinders of a respective cylinder pair with its geometric axis having an eccentricity relative to the crankpin axis equal to the eccentricity of the crankpin axis relative to the crankshaft axis, the geometric axis of the discs on each crankpin having a relative angular separation which is twice the relative angular separation of their respective cylinder pairs, adjacent discs being in contact with each other over areas bounded between their superimposed peripheries as viewed in directions parallel to the crankshaft axis and rigidly connected to each other within said areas whereby all the discs on a common crankpin rotate together, the periphery of each disc being adapted to take a bearing load, and each disc being received in a bearing aperture of a rigid yoke which extends perpendicularly to the crankshaft axis and symmetrically on both sides of the disc, there being in each cylinder a piston connected to each end of the yoke and the yoke being supported against side loads solely by cooperation of the piston with the cylinders at the ends of the yoke, the piston having a substantially fluid-tight seal with the respective cylinder and also includng a hard metal flexible bearing shim about the periphery of said piston and moving therewith, annular insert means engaging said piston disposed at opposite ends of said bearing shim to restrain axial movement of said shim on said piston, said bearing shim having an outside diameter larger than said piston and serving to act as essentailly the sole bearing member for adsorbing any side loads on the piston, by promoting the formation of a film of lubricant under pressure between the outer surface of the shim and the adjacent portion of the cylinder wall at relatively low piston speeds and forming said lubricant film to a wedge-shape (in axial cross section) with the wider end of the wedge facing the direction of movement of the piston at higher piston speeds, there being no gear or gear-train connection between any of the discs and any part of the frame or the crankshaft.