movable in the direction of the double headed arrow 210 this threaded spindle 212 is articulated at its left end shown in fig5 at location 214 at the flap 196 by means of a fitting or bracket 216 acting as a lever the adjustment or positioning motor 208 is connected by an angle bracket 218 or equivalent connection means with the duct or conduit 202 this adjustment or positioning motor 208 can for example drivingly rotate a spherical or ball nut or nut member cooperating with the threaded spindle 212 so that this threaded spindle 212 is reciprocatingly driven for lengthwise movement in the direction of the double headed arrow 210 furthermore this adjustment or positioning motor 208 is rotatably connected at its end facing away from the fitting or bracket 216 with the angle bracket 218 by means of a shaft or axle 219 arranged substantially parallel to the lengthwise axis of the hinge or pivot means 204 in this exemplary embodiment of false air infeed unit or device 220 which incidentally can be employed for instance with the false air openings or infeed openings 26 36 64 and 66 previously considered is constructed as a short duct or conduit section which can be connected by the duct flanges 222 and 224 with and between further duct.