| 摘要 |
A positive displacement fluid handling apparatus has a first, high volumetric displacement rate scroll pump of nested interacting pairs of fixed and movable spiral-shaped blades supported in a housing between an inlet and an outlet. Each adjacent blade pair is of sufficient angular extent, preferably only about 360 DEG , to close an inter-blade pocket. In a preferred form for a vacuum pump, a second scroll pump mounted in the housing has its fluid inlet in direct fluid communication with the first scroll outlet. The second scroll has a single pair of co-acting fixed and movable blades with multiple revolutions with a relatively short axial height. The low back leakage of this second pump allows the first pump to omit tip seals on the free spiral edges of the blades. The volumetric displacement rate of the first pump exceeds that of the second pump. An orbiting plate carries the movable blades of both scroll pumps. The drive has a small crank radius which reduces seal velocity and wear, and reduces radial crank force. Ball thrust bearings held between recesses in the periphery and in the plate offset axially directed compressive forces while synchronizing the orbiting movement. A fan mounted on the drive air cools the apparatus. There is no oil or other liquid lubricant or coolant exposed to the working fluid.
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