Screw Vacuum Pump: A rotary screw pump is one of the earliest designed positive displacement pumps which was referred to as the Archimedes‘ screw. In its most basic variety, this pump includes only one screw within a hollow cylinder. Fashionable designs include double or triple screws meshing versus each other. https://trevorckno902346.activoblog.com/26954510/not-known-factual-statements-about-vacuum-pump