Screw construction

The amount of material extracted from a flooded region by a screw feeder is mainly determined by the screw construction at the outlet end of the infeed region interface. The restraint offered by material in the clearance space between the flight tip and the casing as the screw leaves this region affects whether extra material is carried out by the boundary layer. This section of casing adjacent to the exit point of the screw from the supply hopper is termed the choke section . 

There is, however, a ftorther complication arising from centre shaft contact with standard forms of feeder screw construction. Rotation of the screw shaft makes no contribution to moving the material forward in fact it... 

Table 2-4. Common Materials Used in Screw Construction (100). 

Figure 7.20 Typical flexible screw construction (Spiroflow Ltd).

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