| 摘要 |
Apparatus for extrusion of a plastics pipe, comprising a plurality of different layers is disclosed, including an extrusion die having a base-plate with a mandrel extending therefrom, a stack of five annular die plates secured to the base plate and defining with the mandrel an annular extrusion passage leading to an annular extrusion outlet. Three annular plenum chambers defined respectively between the mandrel and the rearwardmost plate and between adjoining said plates lead into the annular extrusion passage upstream of the extrusion opening. Equalization rings and a front die member are adjustable diametrally with respect to the mandrel to adjust the concentricity of the different layers in the pipe produced. Molten plastics material may be fed from a single source to the rearwardmost and the forwardmost plenum chamber feeding the material for the inner and outer layers of the pipe via a distributor having separate flow adjusters for each of two conduits connectable with the rearwardmost and forwardmost plenum chambers. |
