Heating devices

Claim 1

An airplane heating device to be located aboard an airplane in flight, said device including a. a light weight rigid, self-supporting panel which generates heat uniformly over a board area, b. said panel being composed of i. a flexible heating areal foil embedded in ii. an electrically nonconductive insulating sheet which covers both broad surfaces of the foil and acts to electrically isolate the foil from its physical surroundings; c. said flexible heating foil having a positive resistive coefficient, d. said sheet being water impermeable to waterproof the foil and being thin so that the temperature drop across the sheet during operation of the device is negligible, e. a light weight stiff thermally resistant core of a good thermal insulating characteristic on which the embedded foil is disposed, f. means to secure the embedded foil to a broad surface of the core which is the exterior surface of the core, and g. thin, rugged, tough, water impervious protective covers to complete the panel, said covers having a negligible temperature gradient during operation of the device, h. one said cover covering the surface of the embedded foil remote from the core and the other cover covering the surface of the core remote from the first cover, i. means to secure the covers to the embedded foil and to the core, said foil constituting a flexible electrically nonconductive substrate having a resistance heating layer carrieD thereby, j. said resistance layer having a solid electrically nonconductive matrix through which there is uniformly dispersed a mass of electrically resistive particles k. said electrically nonconductive insulating sheet constituting a flexible electrically nonconductive substrate embedded with a temperature resistant resin, and l. conductive terminals connected to spaced points along edges of the foil and electrical leads connected to said terminal.