Electric self-defrosting windshield heating arrangement providing fast or slow heat

摘要

An electrically heatable self-defrosting windshield has a transparent panel, two low-resistance groups of wires embedded in the panel and defining a primary zone requiring rapid heating, and at least one high- resistance group of wires embedded in the panel and defining a secondary zone adjacent the primary zone and not requiring rapid heating. A switch connected to the wire groups and to an electric power source is movable between a fast-heat position connecting the two low-resistance groups in parallel with each other across the source and effectively disconnecting the high-resistance wires, and a slow-heat position connecting the two low-resistance groups in series with each other and jointly in parallel with the high-resistance groups across the source. The total resistance of the groups in the fast-heat position is generally the same as in the slow-heat position. Each wire group has a pair of transverse buses flanking the respective zone and connected to the switch means and the wires of each group extend longitudinally and generally parallel to one other between the respective buses.