Abstract: A pumping unit having a pump chamber with a rotor mounted in a rotatable manner within the chamber. The pumping chamber is formed by a circumferential wall and two end walls. The circumferential wall is formed on an annular collar of a pump part and has on its inner surface a track on which sealing bodies of a rotor roll. To avoid deformation of the pump part by hydraulic forces or by pressing-in forces, ribs are arranged on the outer surface of the circumferential wall which extend away from the pump chamber. A shoulder is arranged on the side of the end wall which is directed away from the pump chamber. The shoulder is connected by a press fit to the pump housing and has thin walls so that pressing forces do not result in any deformation to the end wall of the pump chamber.

Abstract: A pumping unit having a pump chamber in which a rotor is mounted in a rotatable manner, and which is formed by a circumferential wall and two end walls, is already known. The circumferential wall is formed on an annular collar of a pump part and, on the inside, forms a track on which sealing bodies of a rotor roll. The track of the pump chamber is subjected to high compressive loading which, if the pump part is made of plastic, may result in the track rupturing. In the case of the pumping unit according to the invention, the pump part is improved in respect of strength and service life. Deformation of the pump part by hydraulic forces or by pressing-in forces is avoided.