Rotary vane: Rotary vane pumps are comprised of a number of vanes that are mounted to a rotor that turns inside a cavity. As the vanes rotate, centrifugal push extends them from their individual slots, forming compression cells that get larger to draw air flow in from the intake and smaller to force air flow out the exhaust.
Articulated piston: An articulated piston commercial vacuum pump functions in a way similar compared to that of an automobile engine. As the piston moves downward in the cylinder, atmosphere is used through the intake valve. Through the piston’s Industrial Vacuum Pumps upward stroke, the atmosphere is permitted to flee via an exhaust valve. Two spring-backed piston rings are accustomed to seal the piston to the cylinder.
Screw: Rotary screw pumnps include two parallel rotary screws in the pump casing. The screws are synchronized to turn in opposing directions, which in turn causes the compression action to occur. The 
gas is definitely compressed in direction of the pump’s discharge port.
Liquid ring: Liquid ring pumps also operate via positive displacement. During operation, the pump’s impeller rotates inside the pump casing. A rotating liquid band then seals the impeller and its blades. Liquid is usually sucked into the compression chamber to keep the ring stable. Conveyed gas is certainly compressed during each impeller revolution.
Claw: Claw vacuum pumps consist of two rotors that are extremely close but usually do not are exposed to one another during rotation. As the rotors switch they actually enlarge the space between them to attract air, then because they rotate around, actually decrease the space between them to compress the air flow out of the chamber.