A scraper flight conveyor for preheating thermoplastic bulk material and feeding it to a screw extruder comprises a succession of controllably heated slideways arranged in superposed series, a plurality of scraper flights in sliding contact with each slideway and spaced along a path of travel over the surface thereof, and a drive operable to move the scraper flights on each slideway along the path of travel. The scraper flights push discrete portions of the thermoplastic bulk material along the path of travel. The delivery rate of the material to the slideways is controlled.
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