lateral surface 11 fig2 again illustrates in a diagrammatic side view the parallel orientation of tongues 15 of first part 7 of adapter unit 5 pushed onto second part 9 in the relaxed state the groove shaped profiling of outer lateral surface 11 constituted by an elastomer can also be seen fig3 shows a longitudinal cross section through adapter unit 5 from fig1 and 2 it can clearly be seen in fig3 that second part 9 is constituted conical at least in sections on its inner lateral surface the second part is fastened in particular screwed to a stator 17 see fig4 to 8 of a pump unit 3 conically constituted second part 9 is matched adaptively to the shape of respective stator 17 perforation 13 of first part 7 and perforation 13 u2032 of second part 9 can again clearly be seen in the longitudinal cross section of fig3 perforation 13 of first part 7 and perforation 13 u2032 of second part 9 are aligned in the longitudinal direction of adapter unit 5 and thereby form a channel through which the liquid medium can pass through adapter unit 5 during transport out of the bore first part 7 and second part 9 comprise bores which in the position of first part 7 and second part 9 represented in fig3 are orientated in alignment with one another first and second part 7 9 are connected to one another in a friction.