Summary of the twin screw extruder
Summary of the twin screw extruder
It is an object of the invention to design a twin screw extruder so that it will deliver the melt at a temperature and viscosity largely uniform over the entire cross section area, to a closed tool. According to the invention the twin screw extruder is designed with an extruder housing having a dual cylinder shaped internal cross section. Two extruder screws are located in the housing configured to be driven in opposing directions. The screw turns and screw lands of the extruder screws and transport an extrusion material to an extruder outlet or a molding tool attached to the extruder. During transport the material is heated and plasticized.
According to the single screw extruder a homogenizing zone includes housing part which extends the extruder housing. Extension of the extruder screws, referred to herein as cell rotors, are located in the housing part. The extruder screw/cell rotor combinations rotate in opposing directions. The homogenizing zone may be a unit located in between an extruder screw discharge and a molding tool or as an integral extension of the twin screw extruder. A plurality of radial cell walls define open conveyor cells. The cells walls are circumferentially disposed on the cell rotors extend parallel to or at an angle relative to the rotor axis. The cells walls of one rotor engage the conveyor cells of the other rotor in a contactless meshing manner.
According to the screw extruder, the screw turns of thesheet production extruder may terminate at an axial distance in front of the leading edge of the cell walls in a manner such the cell walls are preceded by a free annular space. Each cell rotor may carry five, six or seven conveyor cells on its circumference. Each conveyor cell may have a rounded arc like profile. The profile may be essentially a circular arc; the arc radius may be 0.18 to 0.3 times the external diameter (D A ) of the rotor. At least the frontal side of the cell walls facing the incoming flow may be sharpened in the manner of a blade.
Advantageously, the cell walls may have one or more interruptions or breaks over their axial length. The interruptions of adjacent cells walls may be located in identical radial planes, so that in the area of the interruptions the cell walls define free annular spaces. Alternatively, the interruptions of adjacent cell walls may be mutually off set in the axial direction. Furthermore, the longitudinal centers of the interruptions may be located on a helical line.
It is an object of the invention to design a twin screw extruder so that it will deliver the melt at a temperature and viscosity largely uniform over the entire cross section area, to a closed tool. According to the invention the twin screw extruder is designed with an extruder housing having a dual cylinder shaped internal cross section. Two extruder screws are located in the housing configured to be driven in opposing directions. The screw turns and screw lands of the extruder screws and transport an extrusion material to an extruder outlet or a molding tool attached to the extruder. During transport the material is heated and plasticized.
According to the single screw extruder a homogenizing zone includes housing part which extends the extruder housing. Extension of the extruder screws, referred to herein as cell rotors, are located in the housing part. The extruder screw/cell rotor combinations rotate in opposing directions. The homogenizing zone may be a unit located in between an extruder screw discharge and a molding tool or as an integral extension of the twin screw extruder. A plurality of radial cell walls define open conveyor cells. The cells walls are circumferentially disposed on the cell rotors extend parallel to or at an angle relative to the rotor axis. The cells walls of one rotor engage the conveyor cells of the other rotor in a contactless meshing manner.
According to the screw extruder, the screw turns of thesheet production extruder may terminate at an axial distance in front of the leading edge of the cell walls in a manner such the cell walls are preceded by a free annular space. Each cell rotor may carry five, six or seven conveyor cells on its circumference. Each conveyor cell may have a rounded arc like profile. The profile may be essentially a circular arc; the arc radius may be 0.18 to 0.3 times the external diameter (D A ) of the rotor. At least the frontal side of the cell walls facing the incoming flow may be sharpened in the manner of a blade.
Advantageously, the cell walls may have one or more interruptions or breaks over their axial length. The interruptions of adjacent cells walls may be located in identical radial planes, so that in the area of the interruptions the cell walls define free annular spaces. Alternatively, the interruptions of adjacent cell walls may be mutually off set in the axial direction. Furthermore, the longitudinal centers of the interruptions may be located on a helical line.