Screw conveying

Abstract

The modern screw conveyor is essentially a development of the well-known Archimedean screw which was conceived some 2000 years ago as a means of raising water for irrigation. Applications of this device were naturally very limited until relatively recent times, and its evolution has consequently been slow. A fundamental feature of the original pattern of Archimedean screw which distinguishes it from other types of screw conveyor is that the helical screw (or ‘flight’) is attached to the inner surface of the cylindrical casing and rotates with it (Figure 10.1). It will be noted from the diagram that the Archimedean screw operates effectively as a positive displacement elevator, the angle at which it will work successfully depending upon the diameter of the casing and the pitch of the screw.