Electrically heated window

An electrically heated window having a transparent portion, the window being in the approximate shape of a trapezium and comprising:

• at least two plies of sheet glazing material,
• at least one ply of interlayer material, the electrically heated window being laminated from said plies of sheet glazing material and interlayer material with the ply of interlayer material extending between the plies of sheet glazing material,
• an array of fine, closely spaced wires carried by one of said plies,
• at least some of said wires extending along diverging lines and fanning out so that the array extends over substantially all of the transparent portion of the window,
• electrical connection means for connecting the array to an electrical supply so as to pass current through the wires and heat substantially all of the window.

A process for the manufacture of an electrically heated window laminated from at least two plies of sheet glazing material and at least one ply of interlayer material, the window including an array of fine, closely spaced wires, wherein part of the process is performed on an apparatus which includes an endless support surface, rotatable about an axis, for supporting the interlayer material, and a wiring head for supplying wire and laying it on the interlayer material, the support surface and wiring head being movable relative to each other in a direction parallel to said axis, and the process including the steps of:

• securing a piece of interlayer material on the support surface,
• causing the support surface to rotate,
• laying wire by setting the wire in contact with the interlayer material by way of the wiring head while the support surface rotates, so that successive turns of wire are laid on the interlayer material;
• moving the support surface and the wiring head back and forth relative to each other in a reciprocating manner in the direction parallel to said axis, and in coordination with the rotation of the support surface, to provide an array of wires on the interlayer material in which at least some of the wires extend along diverging lines and fan out,
• stopping rotation of the support surface when a desired number of turns of wire has been laid,
• cutting the coil in a direction parallel to the axis, so that it may be opened out as a generally flat array of wires,
• removing the wired piece of interlayer material from the support surface and providing the array of wires with electrical connections, and
• assembling the piece of interlayer material into a laminated window.

An apparatus for forming an array of wires on a piece of interlayer material during the manufacture of an electrically heated window, the apparatus comprising:

• an endless support surface for supporting the interlayer material,
• rotating means to rotate the endless support surface about an axis of rotation,
• a wiring head for supplying wire and laying it on the interlayer material, the support surface and the wiring head being arranged for relative movement in a direction parallel to said axis of rotation,
• drive means for reciprocating the support surface and wiring head relative to each other in said parallel direction, and
• control means for controlling the drive means to co-ordinate the reciprocating movement of the support surface and wiring head with the rotation of the support surface, so that the wiring head lays wire along diverging lines which fan out.