Improvements in or relating to mechanical high vacuum pumps of the roots blower type

摘要

953,799. Rotary pumps. W. C. HERAEUS G.m.b.H. July 25, 1960 [Aug. 11, 1959], No. 25792/60. Drawings to Specification. Heading F1F. A high vacuum pumping system for producing a vacuum below 20 Torr comprises a preliminary pump in series with a Roots pump the rotors of which have a cross-sectional shape which has convexly curved end portions and inter-connecting portions which are not concave i.e. the sides may be parallel or convexly curved giving oval-shaped rotors.