| 摘要 |
1370854 Tube extrusion die ARMOSIG 25 May 1972 [26 May 1971] 24758/72 Addition to 1315585 Heading B5A An extruded tube 12, of expanded polyvinyl chloride, is sized in passage through a sizing die 3, to which it is delivered from an extrusion die having an annular flow passage the external and internal diameters of which, in the downstream direction, progressively increase (L1), are substantially constant (intermediate L1 and L2), progressively decrease (L2) with the de. crease of the external diameter being at least 30%, and are constant at the die extrusion outlet passage (L5), with a section L4 intermediate L2 and L5 in which the internal diameter increases, and the external diameter is constant over at least part of the length of the section along which the passage section area preferably decreases by 10 to 40%. The combined length of sections L4 and L5 is 10 to 50 times the thickness of the sized tube. The sizing die 3 is fluid cooled, via conduits 15, the sizing diameter D thereof is 20 to 40% greater than the diameter D3 of the extrusion outlet, and the die 3 may be employed with a pressure within the extruded tube of atmospheric or above, or with vacuum sizing. The extruded tube may be moulded by blowing. |
