Planar electrical food warmer

Claim 1

A food warmer comprising a hermetically sealed shell made of a thermoplastic resin, said shell having a flat upper surface and a flat heating element therebelow, said heating element comprising a conductive sheet and strip electrodes attached to the opposite edges thereof, said conductive sheet comprises a conductive coating deposited on an insulating layer and having a resistance between about 25 and about 100 ohms per square, said conductive coating comprising particles of an electrically conductive material and particles of an electrically nonconductive material, said conductive coating and said strip electrodes being sandwiched between and enclosed by said insulating layer and a second nonconductive sheet material, said insulating layer and said second nonconductive sheet material comprising papers made of inorganic fibers, electrical connections passing through a wall of said shell in hermetically sealed relationship thereto, said connections being connected on the interior of said shell to said strip electrodes At opposite edges of said heating element, said sealed shell comprises two separate unitary moldings, all of the sides of said sealed shell being in one molding, said moldings being joined together by thermoplastic junction, the interior of said sealed shell below said heating element containing a thermal insulating material made of inorganic fibers.