Fluid transfer machine with drive shaft lubrication and cooling

The present invention relates generally to a fluid transfer machine, and more particularly to a fluid transfer machine that can be used as a pump or motor. A fluid transfer machine includes a positive displacement, rotary-type pumping mechanism driven by a drive shaft. The drive shaft is lubricated and cooled by locating the drive shaft in a primary flow path in the machine. Fluid is directed from the inlet through a passage that intersects a cavity surrounding the drive shaft, at a location between a pair of journal bearings. The fluid then continues directly to the suction side of the pumping mechanism. The drive shaft could also be located on the pressure side of the pumping mechanism. The primary flow cools and lubricates the drive shaft and drive shaft bearings, and reduces the size and complexity of the machine, as additional cooling and lubrication flow passage(s) are not required.