Piston pump

Piston pump (10) has stepped piston (50,50') in a stepped bore (39,40), of the holding fixture (3), within a cylindrical socket (50,50'), which is movable in an axial direction Ax. Stepped piston is designed at one end (51,51') partially like hollow tubing fitted at the outer boundary which limits a displacement area (24,25) and carries seal arrangement (26,26') at the center. In the axial direction Ax at one side exists a step (52,52') of stepped piston and on the other side exists spring cage (53,53'). Radially inside the seal arrangement is a flat support (54,54') for flat support shank (55a,b,c;55a,b,c'). The spring cage is fitted orthogonal in axial direction Ax with flat support shank. The stepped piston has a graded bore (56,56') radially inside the support, which ingest the bore, centering shank (57a,b,c;57a,b,c') and spring cage. A spring linked valve body of check valve is arranged coaxially as well as within the graded bore, which serves the ventilation of the displacement area. A reset spring is fitted in the displacement area which is supported on one side at the counter bearings (41) and spring cage on the other side. The bush (18,19) has a stop (63,63') for the stepped piston at one end which is smaller than the diameter of stepped piston in radial direction and at opposite end of bush is fastened a thrust bearing (41) for the piston reset spring, so that stepped piston, reset spring, check valve and seal assembly is arranged as independently manageable group.