heseare oil - immersed, rotary vane type pumps. The rotor with two spring loadedvanes is mounted eccentric in the stator body. As the rotor rotates, the vanessweep the crescent shape air space twice in each revolution. There is inbuiltnon-return valve which prevents back flow of air. All moving parts are manufacturedfrom graded material. These parts are precisely machined, ground and assembledwith close tolerances which results in increased efficiency and long troublefree operating life.