Electrically heated window

Claim 1

A window comprising two sheets of glass and an intermediate layer of transparent plastic all adhered together, said sheets having a trapezoidal shape, a plurality of heating units each including a plurality of electrically conducting resistive filaments, the filaments of all of said units extending substantially parallel to a base of said trapezoidal shape and occupying together a substantially trapezoidal space geometrically similar to said trapezoidal shape, said window further including a plurality of bus bands each connected to the filaments of two of said pluralities whereby the filaments of each of said heating units are connected electrically in parallel and said heating units are connected electrically in series in a zigzag pattern extending from one end of one base of said shape to one end of the other base of said shape, two electrical terminals, a bus band connecting the filaments of a first of said units to one of said terminals, and a bus band connecting the filaments of a last of said units to the other of said terminals, said filaments and bus bands being embedded in said layer of plastic material, the said bus bands, other than those connecting to the said terminals, being divided into two groups with the bus bands of each of said groups being collinearly disposed parallel to one of the inclined sides of said trapezoidal shape.