| 摘要 |
<p>. An extruder assembly (1) for extruding round, cylindrical plastic pipe having a smooth inner pipe wall and a ribbed or ridged outer pipe wall, comprising a feed screw (2) for transporting and softening the plastic material (4), and an annular nozzle having a central mandrel (6). The mandrel constitutes a cylindrical, coaxial extension of the feed screw. The mold part (8) of the nozzle is provided with one or more parallel, helical grooves (14) with the spiral extending in the direction of rotation of the screw and mandrel, and the mold part (8) is provided with a lubricating device (17) for lubricating the molding surface of the mold part. A calibrating device (271 with helical grooves (28) is provided downstream of the annular nozzle. The lubricating device (17) consists of slots (21) between parts of the outer mold wall, which parts are movable in relation to each other for adjusting the slot width. The slot or slots (21) are connected to a source of lubricant (19) which supplies lubricant under pressure. The movable parts may consist of annular disks (20). The radial end surfaces of the disks (20) have a roughened surface. The lubricating device is located at a nozzle section having a plane, circular molding surface and is arranged upstream of the part that is provided with helical grooves. The grooves (28) of the calibrating device (27) have a larger axial width than the pipe ribs formed by the molding tool (8). The grooves (28) also have a larger radial height than the ribs (15) on the pipe (16). The grooves (28) in the calibrating device (27) receive a direct supply of cooling liquid through one or more slots (20) in the calibrating sleeve. The free end of the mandrel (6) projects outwardly beyond the end of the calibrating device (27), and the end section (6') of the mandrel is preferably slightly conically tapered.</p> |
