Abstract: In pumps for conveying gases and providing a differential pressure between the pump inlet and outlet, a pumping space within the pump is hermetically sealed from the pump drive unit. No oil or grease-lubricated parts are located within the pumping space. Accordingly, the pump can be characterized as completely dry running. The hermetical seal is provided by a hollow or tubular member (5) capable of torsion movement and located between a shaft (1) and a container (6). A drive unit (7) connected to the shaft provides it with an oscillating rotary motion transmitted through the shaft to the container (6). Segmented pistons (8a, 8b) are located on the container and oscillate in the pumping space between stationary parts (10a, 10b) and afford the pumping effect.

Abstract: A molecular pump of the Hollweck type is composed of a plurality of stages in order to improve the pumping characteristics. Rotor and stator consist of different portions which are provided alternately with helical grooves and with smooth outer and inner surfaces respectively. The cooperating surfaces of the individual rotor and stator portions are tapered.

Abstract: A turbo-molecular pump has stator discs 2 separated from one another by spacer rings 3 constructed in such a manner that gases streaming back can re-enter the suction space 8 through reduced portions 5 at the outer diameter and through radial recesses 6. Inner reduced portions 7 serve for the additional location of the stator discs 2.