Flow control device, characterized by a) a flow channel composed of non-magnetic material having a center axis (MA), with aa) a first length segment (L1) having a first diameter (D1), ab) a second length segment (L2), wherein the flow channel expands conically from the first diameter (D1) to a second diameter (D2) in the second length segment (L2), and ac) a third length segment (L3), b) a magnetic closing ball (K), which is movably arranged in the second and third length segments (L2, L3) and has a ball diameter (DK) that lies between the first and the second diameters (D1, D2), c) a first, axially polarized (north-south) ring magnet (NSRM), which is oriented centrally in the center axis (MA) and is arranged so as to be longitudinally movable along the center axis and has an inside diameter (RMDI) that is greater than the outside diameter of the flow channel in the third length segment (L3), d) a preloading device (VE), which axially urges the north-south-polarized first ring magnet (NSRM) toward the first length segment (L1), the preloading device (VE) is designed as a reverse-axially-polarized second (south-north) ring magnet (R2), supported on the flow channel , which is oriented centrally to the first ring magnet (R1) on the center axis (MA), characterized in that the preloading device (VE) is designed as an axially-polarized third (north-south) ring magnet (R3), supported on the flow channel, which is oriented centrally on the center axis (MA), wherein a spacer (AH) is arranged between the two mutually attracting ring magnets. a) a flow channel composed of non-magnetic material having a center axis (MA), with aa) a first length segment (L1) having a first diameter (D1), ab) a second length segment (L2), wherein the flow channel expands conically from the first diameter (D1) to a second diameter (D2) in the second length segment (L2), and ac) a third length segment (L3), aa) a first length segment (L1) having a first diameter (D1), ab) a second length segment (L2), wherein the flow channel expands conically from the first diameter (D1) to a second diameter (D2) in the second length segment (L2), and ac) a third length segment (L3), b) a magnetic closing ball (K), which is movably arranged in the second and third length segments (L2, L3) and has a ball diameter (DK) that lies between the first and the second diameters (D1, D2), c) a first, axially polarized (north-south) ring magnet (NSRM), which is oriented centrally in the center axis (MA) and is arranged so as to be longitudinally movable along the center axis and has an inside diameter (RMDI) that is greater than the outside diameter of the flow channel in the third length segment (L3), d) a preloading device (VE), which axially urges the north-south-polarized first ring magnet (NSRM) toward the first length segment (L1), the preloading device (VE) is designed as a reverse-axially-polarized second (south-north) ring magnet (R2), supported on the flow channel , which is oriented centrally to the first ring magnet (R1) on the center axis (MA), characterized in that the preloading device (VE) is designed as an axially-polarized third (north-south) ring magnet (R3), supported on the flow channel, which is oriented centrally on the center axis (MA), wherein a spacer (AH) is arranged between the two mutually attracting ring magnets. <EOS>