Patent ID: 7553086

Claim:
A journal foil bearing comprising: a retaining member having an inner surface which defines a shaft opening within which a rotatable shaft is receivable for rotation; and a foil assembly affixed to and lining the inner surface, the foil assembly comprising a plurality of foil sub-assemblies each of the plurality of foil sub-assemblies having multiple foil segments subtending a circumferential segment of the inner surface, each of the foil sub-assemblies comprising: an under foil sandwiched between a spring foil disposed radially outwardly of the under foil, and a top foil disposed radially inwardly of the under foil, each foil segment of the under foil, the top foil, and the spring foil each having a leading edge distal from a trailing edge in a direction of rotation of the rotatable shaft, and each foil segment of the under foil, the top foil, and the spring foil being affixed to the retaining member along their respective leading edge, their respective trailing edge, or both their respective leading edge and their respective trailing edge, wherein the top foil has a variable radius of curvature from a leading edge of each foil segment of the top foil to the trailing edge of each foil segment of the top foil, the radius of curvature of the top foil decreases from the leading edge of the top foil to the trailing edge of the top foil.