Thick film PTC heating element for hair-drier - has thick film layer which may have different thicknesses having surface at least partially oxidised

摘要

A flat electrically powered heating element consists of a planar non-conductive carrier (10) with a layer of an electrically conductive substance (11) on its surface which functions as a resistance heater, the conductive substance being applied to the carrier as a paste by thick film techniques, terminations (12) being provided to make contact with the conductive layer. The thick film layer (11) may be constructed so as to have different thicknesses in different zones (13,14). The thick film layer (11) may he heated to oxidise its surface layer so as to make it have a positive temp. coefft.. The oxide may extend over the entire surface layer of the thick film. The oxide may extend throughout the whole depth of the thick film, so as to make the whole body of the element have a positive temp. coefft.. The element may be provided on the blades of a fan.