Differential Feed Screw Design Benefits

Large diameter screw prevents “boring” through product. Defeats product bridging over feed screw. Differential action between fights produces low flow rates with a high screw RPM. Discharge from feeder is uniform and pulse free. Multiple screws having common diameters eliminate feed tube changes and resulting dead zones.

Problem

  • Small capacity feed screws with small diameter (and pitch) prevent uniform and reliable filling of screw flights.
  • Large feed screws with large pitches provide uniform filling of screw flights but create large material discharge pulsation when feeding at low feed rates.
  • Small feed screws installed in a feeder designed for large feed screws create material “dead zones” where stagnant material builds up resulting in flow blockage and preventing complete clean out of the feeder.
  • Typical small diameter feed screws of both single and twin screw design are fragile, easily damaged and generally unreliable in heavy industrial process applications.

Solution

Thayer Scale’s Patented Compound Flight Feed Screw

  • Large pitch of screw’s outer winding assures reliable and complete filling of screw flights.
  • Screw’s differential feeding action assures consistent, precise and reliable feeding of material without pulsation.
  • Large over-wind matches (screws) feed chamber and tube diameter eliminating dead zone areas. No material build-up occurs. Assures reliable flow and complete clean out of material.
  • Solid flight screw with robust over-wind assures reliable performance and long term durability in harsh process environments.

Alternative to twin screws. A forward feed helix and a reverse feed helix concentrically mounted to the same shaft.