The Present Invention Relates to a Single Screw Extruder (1)
Thermoplastics resins are typically formed by extruding the material through a through a die which shapes the material. The raw material is placed in a hopper where it is moved into and through a chamber by a screw. The mechanical action of the feeder screw heats and feeds the material through chamber which is typically in the shape of a barrel. The heated and compressed material is forced through the die at the discharge end of the extruder. The extruded part assumes the cross-sectional shape of a die.
In a single screw extruder, the screw typically has an external diameter corresponding to outer edges of the helical threads or flights. The flights may be under sized in relation to the barrel in the feed or hopper area so as to reduce feedthroat friction. Typically, a single keyway in the shaft area of the screw matches a keyway in a sleeve portion of a drive shaft so that a key positioned in the matching keyways is utilized to transmit rotational movement from the drive shaft to the screw. The key is a separate piece of rectangular metal which fits into the matching keyways. A disadvantage attendant with the use of keys is that they may be lost or misplaced. Also, worn keys can contribute to screw wobble.
In a single screw extruder, the screw typically has an external diameter corresponding to outer edges of the helical threads or flights. The flights may be under sized in relation to the barrel in the feed or hopper area so as to reduce feedthroat friction. Typically, a single keyway in the shaft area of the screw matches a keyway in a sleeve portion of a drive shaft so that a key positioned in the matching keyways is utilized to transmit rotational movement from the drive shaft to the screw. The key is a separate piece of rectangular metal which fits into the matching keyways. A disadvantage attendant with the use of keys is that they may be lost or misplaced. Also, worn keys can contribute to screw wobble.
