A fan, with reversible blades, having a hub receiving the stem of the blades and an inner retaining ring, which has {HEAD ~ outwardly extending projections}, supported concentric with {TAIL ~ the hub} 
A fan , with reversible blades , having a hub receiving the stem of the blades and an inner retaining ring , which has { HEAD ~ outwardly extending projections } , supported concentric with { TAIL ~ the hub }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL