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SCREW CONFIGURATION
Almost all Vincent screw presses use the Interrupted Screw Flight design. The
interruptions leave room for stationary resistor teeth that are mounted outside of
the screen. These teeth go through the screen and reach almost to the shaft of the
screw. This design of screw press stands in contrast to a Continuous Screw
design. The main advantage of the interrupted design is that solids material must
accumulate in the interruptions until sufficient consistency is reached for the solids
to be pushed toward the cake discharge. There is a reduced tendency for the
material being pressed to co-rotate with the screw. Also, there is more agitation
within the press and, consequently, quicker and more thorough dewatering.
The screw starts 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 common. 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 design screw is good for high throughput of materials
which are easily dewatered. Glass and sand are examples.
INTERRUPTED FLIGHTS, RESISTOR BARS, and RESISTOR TEETH.
PIE CUTTING
Sometimes the compression of a screw is reduced, in the field, in an operation
called "pie cutting". This involves cutting pie-shaped segments from certain flights
of the screw, leaving a butterfly (end view) configuration. The modification is done
to avoid excessive compression and jamming. (The "sterile cut" is more drastic.)
Consult the factory for assistance before making this modification.
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