A furnace for energy saving and space reduction used in electronic industry assembly, medical sterilization, or food process application is provided. In the furnace there is a number of trays hinged on a pair of continuous chains which movement is in a circle or oval trajectory, or on the rotating beam mechanism constituting as spider web form. A pair of rings is added to restrain the swing movement of each tray via the mechanical linkage during rotation. A dome formed at the top portion inside the furnace is used as an enclosure where the heated inert gas is almost kept. The electric power for heater and blower can be reduced by the natural convection. An opening is located at the lower portion of the furnace; so the operator can do loading and unloading performance.