Electric air heating element

Claim 1

In combination, a tubular air discharge unit and heating element for a hair dryer, said element being positioned in said tubular air discharge duct in coaxial alignment therewith, said heating element comprising a solid coil-carrier of non-conductive and heat resistant material and including at least four longitudinal fins extending radially outwards from a common center line coinciding with the axis of such an air duct, said fins being of equal thickness and having the major extent of their outer edges serrated by inwardly extending substantially rectangularly shaped sets of notches of at least two different depths, said notches being equally spaced by a common spacing module and adjacent sets of notches having a different common depth so as to be intermittently higher and lower throughout such major extent of such outer edges, said notches being axially staggered by a quarter spacing module in respect of every two fins lying at right angles to one another to provide a helical path for resistor element, and a coil in the shape of a flat ribbon resistor wound helically around said coil carrier with the windings being laid successively in said notches with the ribbon lying in the bottom of the notches and extending parallel to the outer edges of the fins to provide intermittent layers in different parallel planes to provide high heat transfer with low flow resistance and to increase air turbulence around the said coil to facilitate breaking up the air boundary layer and providing at least one crossover of the ribbon.