Cowl for fan and its application to a vehicle motorized fan unit

An improved cowl for a fan, comprising a stationary part formed by a diffuser (10) which has an entrance section followed by an exit section disposed in a downstream direction relative to air flow from said entrance section to said exit section, and which also has in the following order in an upstream direction;

• a fastening base (11), a nozzle-funnel (12) located in said exit section, a connection zone (13), a cylindrical skirt (14) located in said entrance section and joined to said nozzle-funnel (12) by said connection zone (13), and a moving part (20) rotatable about an axis (200), which moving part (20) has a peripheral profiled annular hoop (21) which is intended to be rigidly connected to the blade (22) tips (221) of a helix which is mounted coaxially in said skirt (14) so as to be able to rotate therein, wherein, taking as references the direction of flow and the axis (200), said hoop (21) is delimited by an inner wall (2101), an outer wall (2102) and a rear section (2103), wherein said connection zone (13) is delimited by an inner surface (131) with an upstream limit (1310), and wherein said rear section (2103) of the hoop (21) is situated in a plane (P) which is perpendicular to said axis (200) and which passes practically through said upstream limit (1310) of said internal surface (131) of the connection zone (13).