| 摘要 |
<p>An extruder screw mechanism has a barrel (26) that is heated by heating coils, an internal screw (20), and a cylindrical melt sleeve (30) having a plurality of circumferentially spaced, axially extending, radial slots (34) therethrough located between the external barrel (26) and the internal screw (20). Another embodiment of the extruder has a barrel (26) and an internal screw (65), with the internal screw (65) having either a single central axial bore (89') or a plurality of internal axial bores (89). The internal screw (65) is provided with a plurality of external threads (40), with the threads (40) each having a curved starting portion (70) with a helix angle that has a finite value and gradually increases along an initial portion of the screw until the threads (40/70') are substantially linear and parallel to the axis of the screw (65) along the melting portion of the screw (65); a related embodiment has threadless portion (90) separating the linear threads (70') from the curved upstream threads (70). Circumferentially spaced, axially extending, radial slots (87,87') extend from the outer surface of the screw (65) along the melt section portion of the screw radially inwardly to an associated axial bore (89,89') for removing melted polymer as it forms between solid polymer and a heated surface. <IMAGE></p> |
