US Patent 9823018 Heated shelf apparatus and freeze dry cart using same

A freeze-drying system is disclosed which includes a vented cart configured for operation in a pressure-controlled chamber, and a plurality of heated shelves disposed in the vented cart. At least one heated shelf of the plurality of heated shelves is provided. The heated shelf includes a first planar sheet formed from a thermally conductive material having a top configured to conduct heat to a tray resting on the top, a second planar sheet disposed opposite the first planar sheet, and a heating element secured between the first and second planar sheets. The heating element has a surface disposed in thermally conductive contact with the first planar sheet.