US Patent 7341439 Scroll fluid machine having an adiabatic expansion chamber

A scroll fluid machine comprises a driving shaft having an eccentric axial portion at one end; a fixed scroll having a fixed wrap; and an orbiting scroll having an orbiting wrap and rotatably mounted to the eccentric axial portion of the driving shaft. A gas introduced through an inlet on the outer circumference of the fixed scroll is compressed by a compression chamber between the fixed and orbiting wraps towards the center and discharged through an outlet close to the center. Between the eccentric axial portion and the innermost winding portion of the fixed wrap, an adiabatic expansion chamber is formed thereby cooling the compressed gas right before discharging.