Inhibiting device for the formation of solid dirt on an air outlet

The device has a shutter (1) with two vibration fins (3a, 3b) fixed on a support (2). The fins are of different types and are mounted alternately and vibrate in a different manner. One fin (3a) is connected to the support by N fasteners and the other fin (3b) is connected to the support by N+/-1 fasteners. The support is made of bars that are perpendicular to the axial direction of the fins.