Patent ID: 7244113
Filing Date: 2007-07-17
Classification: F04C,F05C

Abstract:
1. Vacuum pumping apparatus comprising: a scroll set having an inlet and an outlet, said scroll set comprising a stationary scroll element including a stationary scroll blade and an orbiting scroll element including an orbiting scroll blade, wherein said stationary and orbiting scroll blades are intermeshed together defining one or more interblade pockets; a motor; and a crankshaft operatively coupled between the motor and the orbiting scroll element, which produces orbiting movement of said orbiting scroll blade relative to said stationary scroll blade when said motor is energized, said crankshaft comprising a first component of a first material rigidly joined to a second component of a second material, wherein the first component has a first coefficient of thermal expansion and the second component has a second coefficient of thermal expansion that is significantly different from the first coefficient of thermal expansion, and wherein the first and second components have relative axial lengths that provide controlled axial expansion and establish a small, non-contacting gap between the orbiting scroll element and the stationary scroll element during operation of the vacuum pumping apparatus.