be identified where appropriate for the understanding of the invention by corresponding reference numerals each increased by u201c 100 u201d the ejector 200 includes planar venturi nozzles 220 222 224 and three suction stages 212 214 216 with the suction ports 246 and the flap valves 248 250 extending in a plane of nozzle plate 274 in which plane the venturi nozzles 220 222 224 are situated the flap valves 248 250 are shown here in a closed position the flap valves 248 250 may be provided on a separate plate 280 or integrated in the suction stages 214 216 e g in respective grooves 290 as indicated in fig7 in the illustration of fig6 the suction ports 246 and the flap valves 248 250 extend perpendicular to a plane of the venturi nozzles 220 222 224 and the flap valves 248 250 assume their closed position compressed air is introduced in a direction of arrow 30 to draw in suction air that enters the multistage ejector 200 via ports 246 as indicated by arrows 244 the suction air exits together with compressed air through outlet channel 267 the flap valves 248 250 open at a certain negative pressure and close the suction port 246 again when the vacuum.