Electrical heating element intended to be incorporated in an inner lining of an item of clothing or accessory intended to be placed against a part of the human body

Claim 1

An electrical heating element intended to be incorporated into a ski boot inner lining conforming to a human foot, comprising: a thin flexible metal sheet having a thickness in the range of about 0.02 to 1 mm and having a size, shape and flexibility to conform to the contours of a ski boot liner and ski boot, an adhesive on one side of the sheet, a thin ductile copper wire having a diameter in the range of 0.1 to 0.4 mm capable of withstanding repeated bending stresses and stresses resulting from crumpling without fracturing, an insulating lacquer coated on the ductile wire, the insulating lacquer withstanding a temperature higher than the temperature to which the wire is subjected when heated by a flow of electrical current therethrough, the lacquer coated ductile wire being fixed over its entire length by the adhesive to the thin metal sheet to provide a structure capable of withstanding repeated bending stresses, the wire being formed in meanders on the thin metal sheet to reduce the temperature gradient by conducting heat away from the wire by reason of the metal sheet, thereby providing the heating element with a negligible temperature gradient therealong and eliminating hot spots and affording uniform heat distribution by the heating element to the ski boot inner lining.