US Patent 7290771 Bellows seals for thermoacoustic devices and reciprocating machinery

A bellows has an elongated bellows body defined by a flexible wall. The wall encloses a volume and extends between a first end and a second end. The body has a cross-sectional shape and a cross-sectional dimension that are generally constant between the first and second ends. The wall has an axial stiffness and an axial linear mass density. The stiffness and/or density varies generally monotonically between the first and second ends of the bellows body.