Triple-ring extrusion die for solid polyvinyl chloride and foamed polyvinyl chloride tubes, has angled bridging sections with partial radial overlap

摘要

Triple-ring extrusion die for solid unplasticized polyvinyl chloride (uPVC) and foamed PVC tubes comprises relative to the middle ring, an inner (4) and an outer (5) bridging section form a pair. Bridges (4, 5) of a pair, partially overlap, radially. Bridges of a pair, share a common axis and are rotated about it through the same angle, in opposite directions. A radial bore (6) passes through the outer ring (2), a pair of bridges and the middle ring (3), to the inner ring (1). The bore carries measurement- and supply lines. Leading edges of bridges which face the oncoming flow, share a common axis, whereas their trailing edges have disparate axes. The bridge cross section is shaped to facilitate flow.