Appts. for prodn. of laminar tubing - has stacked rings profiled to feed separate plastic melts from bores through homogenising bores to join other melts in main tubing bore

摘要

Appts. for the production of laminated plastic tubular films or pipes has one or more rings to feed the plastic materials for the different layers. The rings are concentric round a mandrel and feed the materials into a laminar bore which forms the tubing/piper. Each ring has a feed bore, an annular gate into the laminar bore and at least one distributing bore from which its material emerges radially at the side. Each distributing bore supplies a ring of material entering the feed bore, and the cross-section of each distributing bore narrows down in the direction of flow. ADVANTAGE - The design eliminates the existing problems of e.g. pressure build-up in the feed bores, difficulty in cleaning, separate nozzles and barrels for the individual layers, difficulty in maintaining feed gaps to close tolerances, varying density and pressure in the individual flow streams, and nozzles with large weight/high cost/complicated assembly and cleaning/long flow paths/risk of decomposition of sensitive materials.