Design of toothed belt driven screw vacuum pumps

Abstract Most screw vacuum pumps use oil-lubricated gears for timing of the rotors. An alternative is a toothed belt to drive and synchronise the screw rotors. In combination with grease-lubricated bearings this drive concept allows the design of completely oil-free pumps. However, belts are less accurate in terms of timing, hence the design of efficient pumps is challenging. In this paper, the development of a new series of belt driven dry screw vacuum pumps is discussed. It covers the overall pump concept including cooling system, material selection and noise damping. Particular attention is paid to the design of the screw rotors with respect to the properties of the belt drive. It is shown that the disadvantage of the inaccurate timing and the need for wide rotor to rotor clearance can be overcome with a high number of wraps. Furthermore, it gives insight to applications and practical field experience.