Abstract: A truck trailer or similar bulk storage area is heated by providing electrical resistance heaters in longitudinally-extending metal ducts extending from and to a short distance below the floor level. Electrical sheet resistance heaters are attached to the underside of the metal plate forming the duct top, each duct is placed between a longitudinally-extending pair of wooden floor boards, and a pair of ducts are placed side-by-side near each edge of the trailer bed or floor of the storage area.

Abstract: An electrical resistance device includes a conductive metal pattern carried on an insulating surface. A portion of the conductive metal pattern includes a two-dimensional array of areas devoid of conductive material ("voids") within a mesh of conductive material. Typically, the voids are hexagonal and are arranged such that the adjacent edges of adjacent hexagons are parallel to each other and spaced apart a distance not more than about 0.10 in. The hexagonal voids typically are arranged so that the centers of sets of three adjacent voids lie on the corners of equilateral triangles.

Abstract: An electrical heater including a semi-conductor pattern (e.g., colloidal graphite ink) printed on a substrate. A conductive ink (e.g., a silver ink) is deposited on the semi-conductor pattern. The conductive ink migrates into the semi-conductor material, provides a superior electrical contact between the conductor (e.g., the silver ink) and the underlying semi-conductor material (e.g., the semi-conductor graphite ink), and essentially eliminates interface resistance. In some embodiments, the semi-conductor pattern is printed on one side of a woven cloth substrate and the conductive ink is printed on the other side.

Abstract: Heating devices, in which a semi-conductor pattern is carried on an insulating surface and a pair of spaced apart electrodes are electrically connected to the semi-conductor pattern, are characterized in that the semi-conductor pattern in at least one heating area of the device defines a two-dimensional array of areas that are devoid of semi-conductor material ("voids") within a continuous "mesh" of semi-conductive material. Preferably, the voids are hexagons arranged with the sides of adjacent hexagons parallel to each other, the centers of adjacent hexagons are at the corners of equilateral triangles, and the overall direction of current flow in the device is not parallel to any of the sides of the triangles.

Abstract: An electrical resistance device includes a conductive metal pattern carried on an insulating surface. A portion of the conductive metal pattern includes a two-dimensional array of areas devoid of conductive material ("voids") within a mesh of conductive material. Typically, the voids are hexagonal and are arranged such that the adjacent edges of adjacent hexagons are parallel to each other and spaced apart a distance not more than about 0.10 in. The hexagonal voids typically are arranged so that the centers of sets of three adjacent voids lie on the corners of equilateral triangles.

Abstract: An electrical heater including a semi-conductor pattern (e.g., colloidal graphite ink) printed on a substrate. A conductive ink (e.g., a silver ink) is dposited on the semi-conductor pattern. The conductive ink migrates into the semi-conductor material, provides a superior electrical contact between the conductor (e.g., the silver ink) and the underlying semi-conductor material (e.g., the semi-conductor graphite ink), and essentially eliminates interface resistance. In some embodiments, the semi-conductor pattern is printed on one side of a woven cloth substrate and the conductive ink is printed on the other side.