Vacuum drying apparatus of circulative preheating type

A vacuum drying apparatus of a circulative preheating type, comprising:

• a working area, containing a material-filling-preheating sub-area, a heating sub-area, a drying sub-area, and a material-discharging sub-area;
• a rotatable frame, rotatably installed in the working area and having four accommodating spaces corresponding to the sub-areas of the working area, respectively;
• a plurality of cylinders, installed in the accommodating spaces of the rotatable frame and corresponding to the sub-areas of the working area, in which the cylinders are defined as a preheating cylinder, a heating cylinder, a vacuum drying cylinder, and a material-discharging cylinder, respectively, according to the sub-areas the cylinders are corresponding to;
• and
• a driving assembly, connected to and thereby driving the rotatable frame to rotate;
• wherein when the rotatable frame rotates, each of the cylinders is moved from a currently corresponding sub-area to an adjacent said sub-area, and the driving assembly comprises an extender and a driver in which the driver is settled at one end of the extender and includes a pushing board and a pushing wing that is rotatably connected to the pushing board.