Screw with Tapered (Conical) Shaft
All screws start with a feeder section of continuous flights. This picks up material in the inlet
hopper and pushes it into the screen section. The feeder section ends at the first resistor
tooth. This feeder section of the screw is followed by compression stages where the flights
have reduced pitch. The reduction in pitch of the flights results in compression of the
material going through the press.
A screw configuration referred to as Sterile Butterfly is occasionally used. Sterile is a
reference to a company, not cleanliness. There are a reduced number of flights on this screw,
and the flights do not wrap as far around the shaft as is normal. This screw design is good
for high throughput of materials which are easily dewatered and might jam the press.
Wing Feeders
Sometimes there are blades welded to the outside tips of the last two flights of the screw.
Called "Wing Feeders", these are mounted parallel to the discharge screen surface. If you
install your own, care must be taken that wing feeders are not made so long that they hit the
face of the cone when the cone is in the closed position.
Long Wing Feeder Knobby Wing Feeder
Wing feeders can serve two purposes: (1) In the case of materials that want to channel out the
discharge of the press, like pineapple and spent brewer's grains, long wing feeders break
up the channeling flow and (2) For abrasive applications, short knobby wing feeders are
provided as sacrificial wear elements.
When certain materials are fed through a screw press, clumps of dry material may
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