A study of the literature on screw conveyers and feeders has been made. Most of the work is concerned with conveying material and in these cases the degree of fill in the trough is kept low to protect intermediate bearings and minimize power requirements. An equally important application for the screw, but one which has received less attention, is its use as a constant rate feeder and in this case the screw is run full. The object of the present work has been to find the effect of various parameters on screw performance at all degrees of fill. Experiments are described in which the effects of screw geometry, speed, filling, and the use of materials with different properties have been investigated.

Unlike most feeders which run in a pipe, the screw used in the present experiments ran in a trough. However, when the channel shape was made cylindrical by putting a half cylinder over the top of the screw, this resulted in very little difference in throughput or in power requirement. With the trough it was possible to increase the throughput by up to 10 percent by raising the hopper outlet to 5 cm above the blades-this was due to material moving along above the top of the blades.

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