the pressure medium space and thus between centre disc 40 and support disc 36 u2032 depends on the pressure value that is present in the interior of the flange 18 on the pressure side the value of this pressure is dependent on the back pressure created by the delivery pressure a diaphragm in the flange 18 picks up this value and transfers it to a fluid in the pipeline 52 which is connected with the fluid in the pressure medium space 48 thus identical pressure conditions exist in the region of the flange 18 at the front end of the free end of the rotor and in the region of the centre disc i e at the joint end of the rotor the equalization of the pressure conditions or an increase of the pressure between the centre disc 40 and the support disc 36 u2032 unloads the sliding joint 44 so that it is operated free of pressure the hydraulic connection between the flange 18 on the pressure side and the pressure medium space 48 is a pipeline 52 which is connected with the pump housing 14 in the region of the support disc 36 the hydraulic connection between the interior of the pipeline 52 and the.