Plastic fabricating machines

Claim 1

AN EXTRUDER FOR WORKING AND EXTRUDING PLASTIC MATERIAL AND INCLUDING A DEVICE FOR CONTROLLING BACK-UP PRESSURE AND DEVELOPING A MIXING ACTION, COMPRISING A BARREL HAVING AN INLET AND AN OULET, AN EXTRUSION SCREW ROTATABLY MOUNTED IN SAID BARREL FOR THE MOVEMENT OF PLASTIC MATERIAL FROM SAID INLET THROUGH SAID BARREL TO SAID OUTLET, A FIRST MIXING MEMBER RIGIDLY CONNECTED TO SAID BARREL ADJACENT SAID OUTLET AND HAVING ON THE INNER FACE THEREOF A PLURALITY OF CONCENTRIC ANNULAR DEPRESSIONS, MEANS IN SAID FIRST MEMBER DEFINING AN AXIAL OUTLET OPENING FOR RESTRICTING THE DISCHARGE FLOW OF MATERIAL FROM SAID EXTRUDER, A SECOND MIXING MEMBER SPACED WITHIN SAID BARREL ON THE DISCHARGE END OF SAID SCREW AND DEFINING WITH SAID BARREL AN ANNULAR SPACE BETWEEN THE OUTER SURFACE OF SAID SECOND MEMBER AND SAID BARREL THROUGH WHICH SUCH MATERIAL FLOWS FROM SAID SCREW TO SAID FIRST MEMBER, MEANS MOUNTING SAID SECOND MEMBER FOR ROTATION WITH SAID SCREW, SAID SECOND MEMBER HAVING A PLURALITY OF CONCENTRIC ANNULAR RAISED PORTIONS CORRESPONDING GENERALLY TO THE CONFIGURATION OF SAID DEPRESSIONS AND PROJECTING AXIALLY INTO SAID DEPRESSIONS IN SPACED APART INTERFITTING RELATIONSHIP EFFECTING DURING ROTATION OF SAID SECOND MEMBER A CONTROLLED BACK-UP PRESSURE, SHEAR, AND MIXING ACTION ON THE MATERIAL AS IT FLOWS INWARDLY BETWEEN SAID MEMBERS FROM THE OUTER SURFACE OF SAID SECOND MEMBER TO SAID AXIAL OUTLET OPENING WITHIN SAID FIRST MEMBER.