Impeller and method for manufacturing said impeller

Claim 1

An impeller especially for fans of cooling systems for internal combustion engines and fans of air-conditioning equipment, comprising root portions formed on the blades to form a closed ring which is engaged by the rim of a hub, particularly wherein one of the two raDial edges of each blade overlaps the adjacent radial edge of the adjacent blade in plan view at the ring of blades, at least in the neighborhood of the blade roots, the improvement characterized in that the two radial side faces of each root portion extend in inclined directions and each make an acute angle, with a radial plane perpendicular to the general plane of the ring of blades, at the associated side of the root portion, so that with the root portions freely in mutual engagement they lie on a line which forms one turn of a helical thread and that of the two radial side surfaces of each root portion one has a projection standing out in the direction of the periphery of the root portion ring, and having an extension in the peripheral direction of the ring which increases progressively from the inner surface of the associated root portion to the associated blade, and the other has a complimentarily formed recess in which the projection of the adjacent root portion engages, so that on mutual engagement of all projections and recesses a closed ring is formed from the said helical line.