Multi-ring die

摘要

A multi-ring die for extruding tubes composed of a plurality of layers comprises a die portion which is composed of a core and at least two rings disposed one around another and defining die passages therebetween and a column-like portion which is equipped with at least two nozzles mounted fixedly on the outer periphery thereof and is formed with passages communicating with the nozzles for feeding resins plasticized at a plurality of plasticizing mechanism into the die passages; each passage in the column-like portion comprising a guide passage and a branch passage having a plurality of branch bores disposed radially. The die of the invention is compact in size and is available even in the apparatus which is adopted for formation of tubes of a single layer. Besides the tube extruded from the die of the invention is even and uniform in thickness.