Screw Vacuum Pump: A rotary screw pump is without doubt one of the earliest created positive displacement pumps which was generally known as the Archimedes‘ screw. In its simplest variety, this pump includes one screw within a hollow cylinder. Modern models include double or triple screws meshing against each other. https://gregoryrkaly.total-blog.com/the-best-side-of-air-compressors-51941757